Elephant Formulary

© 2003-17 Susan K. Mikota DVM and Donald C. Plumb, Pharm.D. Published by
Elephant Care International

Disclaimer: the information on this page is used entirely at the reader's discretion, and is made available on the express condition that no liability, expressed or implied, is accepted by the authors or publisher for the accuracy, content, or use thereof.



Elephant specific information, if available, is in blue.

Technical information to be added.


CAUTION!  Sedative and anesthetic drug dosages for African elephants often vary from those for Asian elephants.  Do not assume that the recommendations for one species can be applied to the other.  Significant variation may also occur between individual elephants.  Higher doses may be needed in wild or excited animals. Unless otherwise specified, doses refer to captive elephants.  The information provided here should be used as a guideline only.  Consultation with experienced colleagues is advised.


SPECIAL NOTE REGARDING ETORPHINE: Opioid narcotics elevate blood pressure and have been implicated in the etiology of pink foam syndrome in wild African elephants.  This emergency situation can be fatal. The syndrome manifests as pink froth from the trunk and is caused by pulmonary edema and capillary bleeding. Several authors recommend that azaperone be combined with opioid narcotics to counteract these hypertensive effects (see Hattingh and Knox, 1994 below).  See azaperone monograph for further information.


Elephant doses:

a) African elephants: 0.003 mg/kg etorphine; antagonize with 3 mg diprenorphine per mg etorphine given; Asianelephants: 0.003 mg/kg; supplement with 2 mg etorphine as needed to maintain immobilization; antagonize with 0.012 mg/kg diprenorphine (Kreeger, 2002).


b) 1 mg/1000kg IM for recumbency and surgical anesthesia in captive Asian elephants (Nayar et.al. 2002).


c) 12 mg etorphine and 150 mg azaperone for capture of wild African elephant bulls. See original work for cow and juvenile doses. The author notes that old females and lactating females tend to recycle etorphine and should be reversed first prior to loading and transfer (du Toit, 2001).


d) Five adult female wild African elephants (approx. 3000-3500kg) were immobilized with 10 or 12 mg (28-40 µg/kg) etorphine and reversed with 1000 or 1200 mg naltrexone (100 times the etorphine dose). (Horne et.al. 2001).


e,f) A 2817 kg female Asian elephant was induced with 1.75 mg etorphine IM, followed by 0.75 mg etorphine at 40 minutes. The elephant was  intubated with a 30 mm endotracheal tube and maintained with 1.5-2.0% isoflurane. Additional etorphine (total additional 1.4 mg) was supplemented IV during the procedure to surgically remove P-3.  Thirty minutes prior to the completion of the procedure isoflurane was discontinued, but oxygen continued to flow.  Additional etorphine was given intermittently IV (0.4 mg total) during the remaining 45 minutes of recumbency.  Naltrexone was given IV and the elephant was standing within 3 minutes. (Fowler et.al. 1999 and 2000).  (Author’s (Mikota) note: the dose of Naltrexone reported in the 1999 publication of this case was 250 mg and the dose reported in the 2000 publication was 60 mg).


g) For capture of adult, wild African elephants, etorphine in combination with azaperone as follows (the peripheral vasodilation effects of azaperone help to reduce the hypertension caused by the narcotic) :

adult females: 12 mg etorphine and 100 mg azaperone

adult males: 15 mg etorphine and 200 mg azaperone

For captive elephants, reduce dosage by 25 %.


For capture of wild African calves, etorphine in combination with azaperone according to shoulder height as follows:

Shoulder height 90 – 115 cm: 2 mg etorphine and 20 mg azaperone

Shoulder height 116 – 140 cm: 5 mg etorphine and 50 azaperone

Shoulder height 141 – 165 cm: 7 mg etorphine and 70 mg azaperone

Shoulder height 166 – 200 cm: 9 mg etorphine and 90 mg azaperone

For captive elephants, reduce dosage by 25 %


To reverse the effects of etorphine, give diprenorphine IV as a single bolus at three times the etorphine dose (Raath, 1999).


h) Following premedication with 120 mg azaperone, two 5-year-old African elephants were given 1 mg etorphine IM as a “walking dose,” and 2 mg etorphine to induce anesthesia.  See abstract below (Stegmann, 1999).


i,n) Twenty free-ranging adult wild African elephants in northern Botswana were immobilized with a mean (±SD) of 9.5 ± 0.5 mg etorphine hydrochloride and 2000 IU hyaluronidase by i.m. dart and recovered uneventfully following reversal with diprenorphine at 23.3±1.5 mg IV and 11.7±0.5 mg IM or 24 mg all IV (Osofsky, 1997).


j) Etorphine (7-15 mg) was combined with azaperone (60-100 mg) and hyaluronidase 1500-3000 IU) in a translocation operation of 26 wild African elephants in central Kenya.  Induction time was 7-15 minutes.  Five elephants died from metabolic changes unrelated to drugs doses administered. (Njumbi et.al. 1996).  (Author’s (Mikota) note: hyalase is incorrectly described as a tranquilizer in this article).


k) For capture of wild African elephants ≤ 600 kg:  etorphine 0.35 ± 0.13 µg/(kg/min) and azaperone 3.11 ± 1.10 µg/(kg/min). For capture of wild African elephants > 600 kg: etorphine 0.23 ± 0.09 and azaperone 2.01 ± 0.8 µg/(kg/min) Note: Total doses of etorphine and azaperone [µg/(kg/min)] were calculated as a sum of the induction (dart) dose and any following supplements divided by the elephant’s body mass and calculated anesthetic/recumbent time.  Body mass of smaller elephants was determined by weighing.  Body mass of larger elephants (>1000 kg) was estimated from shoulder height.  See abstract below.  (Still et.al. 1996).


l) Immobilon® (etorphine + acepromazine): 1mg/450 kg IM for captive Asian elephants (Cheeran,et.al. 1995).


m) For immobilization of captive Asian elephants: 0.002-0.004 mg/kg (6-20 mg total dose); For immobilization of captive African elephants: 0.0015-0.0030 mg/kg (4-20 mg total dose) (Fowler, 1995).


n) see i above


o) Eight African elephants were immobilized with etorphine at a dosage of 3.2 ± 0.5 µg/kg IM. See abstract below (Schumacher et.al. 1995).


p)  Six adult, male wild African elephants (bodyweight approximately 5000 kg) were immobilized, with 8 mg etorphine (M99) for semen collection by electroejaculation (see abstract below, Hattingh et.al. 1994).


q) Etorphine in combination with azaperone to reduce blood pressure.  See abstract below (Hattingh et.al. 1994).


r) Sixteen adult female free-ranging African elephants were immobilized with 11.6 ± 0.3 mg of etorphine (M99) mixed with a standard dose of hyaluronidase (4500 IU). The 16 elephants were reimmobilized again using higher doses of etorphine (standardized at 15 mg total dose) with hyaluronidase (4500 IU) (Kock et.al. 1993).


s) Adult male African elephants: 6-20 mg; adult female African elephants: 4-15 mg. Use lower range doses for elephants under controlled conditions and higher range doses for elephants that are excited, angry, or exerted. The addition of hyaluronidase (4500 IU total dose) is recommended to reduce induction time. The average induction time in free-ranging elephants with doses of 14 mg (females) and 20 mg (males) is 5.38 minutes (range 3.15-10.4 minutes).  Reverse with diprenorphine at 4 times the etorphine dose in mg. The average recovery time is 3 minutes (Kock et.al. 1993).


t) For adult wild African bull elephants: 16 mg etorphine (reverse with 48 mg diprenorphine); for adult cows: 12 mg etorphine (reverse with 36 mg diprenorphine) (Raath, 1993).


u) For the capture of wild Asian elephants:  adult elephants weighing 4 to 4.5 tons require an average of 6.75 mg etorphine; subadult elephants weighing 2.5 to 3.0 tons may require 6 mg. Can use in combination with acepromazine (Immobilon®).  Induction time is 10-12 minutes but will be delayed if injection is SC (Appayya, et.al. 1992).


v) Can be combined with hyaluronidase to reduce induction time (see hyaluronidase monograph for doses).  Hyaluronidase activity remains high for at least 48 hr, provided storage temperatures can be maintained at ≤ 30°C. Storage at ≥ 40°C is associated with rapid loss of enzyme activity (Morton et.al. 1991).


w)  One African elephant was premedicated with an IM combination of 0.27 mg/kg ketamine and 0.23 mg/kg xylazine followed 20 minutes later by 0.9 µg/kg etorphine IV and then halothane.  Two elephants weighing 900 and 3000 kg were trained to lay in lateral recumbency and were given etorphine (mean dose 2.2 µg/kg) IV.  One elephant was intubated and maintained with halothane and the other was maintained by repeated administration of IV etorphine.  Two elephants weighing 750 and 1500 kg received 3.3 µg/kg etorphine IM and following immobilization were intubated and maintained with halothane (Welsch et.al. 1989).

x) Sixteen 3- to 5-year-old African elephants were anesthetized one or more times for a total of 27 diagnostic and surgical procedures. Xylazine (0.1 ± 0.04 mg/kg of body weight, mean ± SD) and ketamine (0.6 ± 0.13 mg/kg) administered IM induced good chemical restraint in standing juvenile elephants during a 45-minute transport period before administration of general anesthesia. After IM or IV administration of etorphine (1.9 ± 0.56 micrograms/kg), the mean time to lateral recumbency was 20 ± 6.6 and 3 ± 0.0 minutes, respectively (Heard et.al. 1988).


y) Fourteen African elephants were immobilized with etorphine (2.9 ± 0.7 µg/kg) and physiological effects compared. See abstract below. (Jacobson et.al, 1987).


z)  Serum etorphine levels were measured in 11 African elephants. See abstract below (Jacobson et.al. 1986).


aa) 1 mg/450 kg for Asian elephants IV or IM; 1 mg/600 kg for African elephants IV or IM. Reverse with 2 mg diprenorphine for every mg of etorphine. It is better to overdose with etorphine than to underdose (Schmidt, 1986).


bb)  An Asian bull in musth (estimated weight 4500 kg) was immobilized six times. Three drugs were used either alone or in combination.  A mixture of etorphine and acetylpromazine (Immobilon®)  was used effectively on three occasions at an average dose of 0.48 ml/1000kg. Xylazine (0.1 mg/kg)  used alone was ineffective on two occasions and was supplemented with Immobilon. When Immobilon® was used after the xylazine, the dose was reduced to 0.2 ml / 1000 kg. Author’s (Mikota) note: xylazine dose given as mg/kg and etorphine dose given as ml in original article (Kock et.al. 1984).


cc) Etorphine (4 mg/ml) was used as the immobilizing agent at a dose of 1 mg per foot (30cm) shoulder height (estimated) on 3 male Asian elephants aged 40-45 years and 255-300 cm shoulder height.  Immobilon® ( 2.45 mg/ml etorphine and 10 mg/ml acepromazine) was used on four subsequent occasions at a dosage of 2.45 mg etorphine and 10 mg acepromazine per 4 ft (120 cm) shoulder height on male elephants aged 30-50 years and 240 –270 cm shoulder height.  Drugs were given IM.  Induction times were 11-18 minutes for Immobilon® and  13-25 minutes for etorphine (Bongso et.al. 1978).


dd) Etorphine (5-8 mg) adequately immobilized four adult Asian male elephants with estimated weights of 3300-3700 kg. Induction times varied from 8 to 19 minutes (Jainudeen et.al. 1971).



Elephant references:

a) Kreeger,T.J., Arnemo,J.M., and Raath,J.P., 2002. Handbook of wildlife chemical immobilization. Wildlife Pharmaceuticals Inc., Fort Collins, Colorado, U.S.A., pp. 183-184
Web/URL: www.wildpharm.com

b) Nayar,K.N.M., Chandrasekharan,K., and Radhakrishnan,K. 2002. Management of surgical affections in captive elephants. Journal of Indian Veterinary Association Kerala 7:(3):55-59

c) du Toit,J.G., 2001. Veterinary Care of African Elephants. Novartis, Pretoria, Republic of South Africa, 1-59 pp.  Web/URL:  www.wildlifedecisionsupport.com

d) Horne,W.A., Tchamba,M.N., and Loomis,M.R. 2001. A simple method of providing intermittent positive-pressure ventilation to etorphine-immobilized elephants (Loxodonta africana) in the field. Journal of Zoo and Wildlife Medicine 32:(4):519-522  
Abstract: Five African elephants (Loxodonta africana) were immobilized with etorphine in 
Waza National Park, Cameroon, for the purpose of deploying radio/satellite tracking collars.  A portable ventilator constructed from two high-flow demand valves and the Y-piece of a large animal anesthesia circuit was used to provide intermittent positive-pressure ventilation with 100% oxygen.  Oxygenation status improved dramatically in all five elephants.  In one hypoxemic elephant, arterial PaO2 increased from 40 to 366 mm Hg.  The results of this study demonstrate that both oxygenation and ventilation can be readily controlled in etorphine-immobilized elephants even under remote field conditions.

e) Fowler,M.E., Steffey,E.P., Galuppo,L., and Pascoe,J.R. 2000. Facilitation of Asian elephant (Elephas maximus) standing immobilization and anesthesia with a sling. Journal of Zoo and Wildlife Medicine 31:(1):118-123  Abstract: An Asian elephant (Elephas maximus) required general anesthesia for orthopedic foot surgery. The elephant was unable to lie down, so it was placed in a custom-made sling, administered i.m. etorphine hydrochloride in the standing position, and lowered to lateral recumbency. General anesthesia was maintained with isoflurane administered through an endotracheal tube. After surgery, the isoflurane anesthesia was terminated, with immobilization maintained with additional i.v. etorphine. The elephant was lifted to the vertical position, and the immobilizing effects of etorphine were reversed with naltrexone. The suspension system and hoist for the sling were designed specifically for the elephant house.

f) Fowler,M.E., Steffey,E.P., Galuppo,L., and Pascoe,J.R.  1999. Standing immobilization and anesthesia in an Asian elephant (Elephas maximus). Proc. Am. Assoc. Zoo Vet. Pages: 107-110

g) Raath,J.P., 1999. Relocation of African elephants. In: Fowler,M.E. and Miller,R.E. (Editors), Zoo and Wild Animal Medicine: Current Therapy 4. W.B. Saunders, Philadelphia, PA, USA pp. 525-533

h) Stegmann,G.F. 1999. Etorphine-halothane anaesthesia in two five-year-old African elephants (Loxodonta africana). Journal of the South African Veterinary Medical Association 70:(4):164-166  Abstract: Anaesthesia of 2 five-year-old female African elephants (Loxodonta africana) was required for dental surgery. The animals were each premedicated with 120 mg of azaperone 60 min before transportation to the hospital. Before offloading, 1 mg etorphine was administered intramuscularly (i.m.) to each elephant to facilitate walking them to the equine induction/recovery room. For induction, 2 mg etorphine was administered i.m. to each animal. Induction was complete within 6 min. Surgical anaesthesia was induced with halothane-in-oxygen after intubation of the trunk. During surgery the mean heart rate was 61 and 45 beats/min respectively. Systolic blood pressures increased to 27.5 and 25.6 kPa respectively, and were treated with intravenous azaperone. Blood pressure decreased thereafter to a mean systolic pressure of 18.1 and 19.8 kPa, respectively. Rectal temperature was 35.6 and 33.9 degrees C at the onset of surgery, and decreased to 35.3 and 33.5 degrees C, respectively, at the end of anaesthesia. Etorphine anaesthesia was reversed with 5 mg diprenorphine at the completion of 90 min of surgery.

i) Osofsky,S.A. 1997. A practical anesthesia monitoring protocol for free-ranging adult African elephants (Loxodonta africana). Journal of Wildlife Diseases 33:(1):72-77   
Abstract: Twenty free-ranging adult African elephants in northern Botswana were immobilized with a mean (± SD) of 9.5 ± 0.5 mg etorphine hydrochloride and 2000 IU hyaluronidase by i.m. dart. The mean time to recumbency was 8.7 ± 2.4 min. All animals were maintained in lateral recumbency. The anaesthesia monitoring protocol included cardiothoracic auscultation; palpation of auricular pulse for quality and regularity; checking of rectal temperature, and monitoring of respiratory and heart rates. Results of basic physiological measurements were similar to those of previous field studies of African elephants immobilized with etorphine or etorphine-hyaluronidase. In addition, continuous real-time pulse rate and percent oxygen saturation of haemoglobin (SpO2) readings were obtained on 16 elephants with a portable pulse oxygen meter. Duration of pulse oximetry monitoring ranged from 3 to 24 min (mean ±SD = 8.2 ± 4.8 min). Differences between minimum and maximum SpO2 values for any given elephant ranged from 1 to 6 percentage points, evidence for relatively stable trends. The SpO2 readings ranged from 70% to 96% among the 16 elephants, with a mean of 87.3 ± 2.8%. 15 of 16 elephants monitored with a pulse oximeter had mean SpO2 values 
 81 ± 2.4%, with 11 having mean SpO2 values ≥ 85 ± 1.5%. All 20 animals recovered uneventfully following reversal: diprenorphine at 23.3 ± 1.5 mg (IV) with 11.7 ± 0.5 mg IM, or 24 mg diprenorphine given all IV.

j) Njumbi,S.T., Waithaka,J., Gachago,S., Sakwa,J., Mwathe,K., Mungai,P., Mulama,M., Mutinda,H., Omondi,P., and Litoroh,M. 1996. Translocation of elephants: the Kenyan experience. Pachyderm 22:61-65

k) Still,J., Raath,J.P., and Matzner,L. 1996. Respiratory and circulatory parameters of African elephants (Loxodonta africana) anesthetized with etorphine and azaperone. Journal of the South African Veterinary Medical Association 67:(3):123-127  Abstract: Respiratory rate, heart rate, blood-gas tensions (PO2 and PCO2) and pH of arterial (a) and peripheral venous (v) blood, concentration of haemoglobin in arterial blood (Hb), saturation of arterial haemoglobin with oxygen and the end-expiratory concentration of oxygen were measured in 22 juvenile African elephants anaesthetized with etorphine and azaperone during 35 to 65 min after they assumed lateral recumbency. Based on these parameters the alveolar-arterial and arterial-peripheral venous differences of PO2 [P(A-a)O2 and P(a-v)O2, respectively], and oxygen content of arterial blood (CaO2) were calculated. Elephants with body mass of ≤ 600 kg showed significant changes in the following parameters compared with elephants with a body mass of more than 600 kg (x ± SD) : PO2 (64 ± 11 compared with 82 ± 8 mmHg), P(a-v)O2 (9 ± 5 compared with 22 ± 9 mmHg), P(A-a)O2 (37 ± 16 compared with 15 ± 8 mmHg) and Hb (148 ± 20 compared with 130 ± 10 g/litre) (p< 0.05). These findings suggested a tendency towards impaired oxygen exchange in the lungs, reduced peripheral extraction of oxygen and elevated oxygen-carrying capacity of arterial blood in smaller elephants. These changes were theoretically attributed to the respiratory-depressant and sympathomimetic effects of higher dosages of etorphine used in the smaller elephants to maintain a clinically acceptable anaesthetic plane. Individual elephants spent 35 to 150 min under anaesthesia and all recovered uneventfully after reversal of etorphine with diprenorphine.

l) Cheeran,J.V., Chandrasekharan,K., and Radhakrishnan,K., 1995. Principles and Practice of Fixing Dose of Drugs for Elephants . In: Daniel,J.C. (Editor), A Week with Elephants; Proceedings of the International Seminar on Asian Elephants. Bombay Natural History Society; Oxford University Press, Bombay, India pp. 430-438

m) Fowler,M.E., 1995. Elephants. In: Restraint and handling of wild and domestic animals. Iowa State University Press, Ames, Iowa, USA pp. 265-269

n) Osofsky,S.A.  1995. Pulse oximetry monitoring of free-ranging African elephants (Loxodonta africana) immobilized with an etorphine/hyaluronidase combination antagonized with diprenorphine. Joint Conference AAZV/WDA/AAWV. Pages: 237-277

o) Schumacher,J., Heard,D.J., Caligiuri,R., Norton,T., and Jacobson,E.R. 1995. Comparative effects of etorphine and carfentanil on cardiopulmonary parameters in juvenile African elephants (Loxodonta africana).  Journal of Zoo and Wildlife Medicine 26:(4):503-507  
Abstract: Fourteen African elephants (Loxodonta africana) were immobilized with either etorphine hydrochloride (3.2 
± 0.5 µg/kg i.m.) or carfentanil citrate (2.4 µg/kg i.m.). Induction time with etorphine was significantly longer (30 ± 21 min) than with carfentanil (8 ± 2 min).  Immediately following immobilization all elephants were placed in lateral recumbency and respiratory rate, heart rate, and rectal body temperature were monitored every 5 min throughout the immobilization period.  Arterial blood samples, collected from an auricular artery, were taken 10 min after immobilization and every 15 min thereafter for up to 1 hr.  At the first sampling, mean values for arterial blood gas variables for etorphine immobilized elephants were pHa, 7.29 ± 0.03; PaCO2, 53.4 ± 5.2 mmHg; PaO2, 71.8 ± 13.8 mmHg; standard base excess (SBE), -1.6 ± 2.9 mEq/L; and HCO3, 25.7 ± 2.7 mEq/L. After 1 hr of immobilization, mean arterial blood gas values were pHa, 7.32 ± 0.06; PaCO, 57.2 ± 9.6 mm Hg; and PaO, 53.8 ± 10.5 mm Hg; SBE, 2.7 ± 1.4 mEq/L; and HCO3-, 30.6 ± 1.6 mEq/L.


For carfentanil immobilized elephants, blood gas values at the first time of collection were pHa, 7.28 ± 0.04; PaCO2, 52.1 ± 2.8 mmHg; PaO2, 78.3 ± 14.7 mmHg; SBE, -2.3 ± 24 mEq/L; and HCO3-, 24.3 ± 2.1 mEq/L.  Sixty minutes after the first sampling, blood gas values of one elephant were pHa, 7.38; PaCO2, 48.7 mmHg; PaO2, 52 mmHg; SBE, 3.4 mEq/L, and HCO3-, 28.8 mEq/L.  Over time there was a progressive decline in arterial PO2 in all elephants.  It is concluded that elephants immobilized with either etorphine HCl or carfentanil developed hypoxemia (PaO2 < 60 mmHg) after 30 min of immobilization.  It is recommended that the administration of one of these opioid drugs be accompanied by supplemental oxygen, or followed by an inhalant anesthetic in 100% oxygen for prolonged procedures.  Diprenorphine or nalmefene reversal was rapid and uneventful in both the etorphine and carfentanil group.  No cases of renarcotization were noted. Additional excerpt: All elephants in the etorphine group (n=8) received diprenorphine at a mean dosage of 8.3 ± 1.1 µg/kg IV. Two elephants in the carfentanil group (n=6) were administered diprenorphine at a dosage of 8.9 µg/kg IV and IM.  Three elephants in this group received nalmefene hydrochloride.  One of the three elephants was given nalmefene 166.7 µg/kg both IV and SC. Two of the three elephants were given nalmefene IV and IM. The dosage was 88.9 µg/kg IV and IM in one elephant and 53.3 µg/kg IV and IM in the other. One elephant in the carfentanil group was administered nalmefene (88.9 µg/kg IV) followed by diprenorphine (8.9 µg/kg IM).


p) Hattingh,J., Knox,C.M., and Raath,J.P. 1994. Arterial blood pressure of the African elephant (Loxodonta africana) under etorphine anaesthesia and after remobilisation with diprenorphine. Veterinary Record 135:(19):458-459  Abstract: Six adult, male elephants (bodyweight approximately 5000 kg) were immobilized, with 8 mg etorphine (M99) for semen collection by electroejaculation. Before electrostimulation (about 10 minutes after the elephants initially became recumbent) their mean arterial pressure was 186 ± 25 mm Hg. During the electrostimulation procedure to which each elephant was subjected intermittently over a period of about 20 minutes using a rectal probe, the mean was 263 ± 30 mm Hg. After 10 to 15 minutes stabilization, 26 mg diprenorphine (M50/50) was administered i.v. The elephants adopted a rocking motion in an attempt to stand up. This motion was accompanied by wide fluctuations in arterial pressure which peaked at 245 ± 19 mm Hg immediately before they rose. Arterial pressure subsequently decreased to a mean of 200 ± 28 mgHg once they were standing. Since these values were higher than that previously observed in standing, conscious elephants (145 ± 3 mmHg) it appears the standing, remobilized elephants in this study were hypertensive. Possible reasons for this are discussed. It is suggested that in view of the observed and possible detrimental increase in arterial pressure during electrostimulation simultaneous blood pressure monitoring should be carried out when this procedure is employed.

q) Hattingh,J. and Knox,C.M. 1994. Arterial blood pressure in anesthetized African elephants. South African Journal of Wildlife Research 24:(1/2)  Abstract: A number of elephants previously captured in the Krueger National Park developed a pink frothy discharge from the external nares. Some of these elephants subsequently died and histopathological examinations indicated severe lung oedema.  In view of the current hypothesis that high blood pressure could be a causative factor, arterial blood pressure was measured in elephants immobilized with etorphine alone (n=71) and with etorphine/azaperone (n=109) and with carfentanil/azaperone (n=26) mixtures. Arterial pressure was found to be significantly lower in the groups immobilized with azaperone mixtures than in the group immobilized with etorphine alone (p < 0.05).  In addition, no cases of lung oedema were observed in animals immobilized with etorphine/azaperone and carfentanil/azaperone mixtures.  It is strongly recommended, therefore, that azaperone be added to immobilization mixtures when elephants are subjected to herding prior to darting. Additional excerpt: all elephants in this study were juveniles 200 to 1300 kg.  Group 1 (n=71) was immobilized with 4-8 mg etorphine; group 2 (n=109) was immobilized with 4-8 mg etorphine and 50-90 mg azaperone; and group 3 (n=26) was immobilized with 4-8 mg carfentanil and 50-90 mg azaperone.

r) Kock,M.D., Martin,R.B., and Kock,N. 1993. Chemical immobilization of free-ranging African elephants (Loxodonta africana) in Zimbabwe, using etorphine (M99) mixed with hyaluronidase, and evaluation of biological data collected soon after immobilization. Journal of Zoo and Wildlife Medicine 24:(1):1-10  Abstract:Sixteen adult female free-ranging elephants were immobilized in July 1990, using a mean (±SE) dose per animal of 11.6 ± 0.3 mg of etorphine (M99) mixed with a standard dose of hyaluronidase (4500 IU), at the Sengwa Wildlife Research Area, Zimbabwe, to attach telemetry and infrasound detection collars. The 16 elephants were reimmobilized in December 1990, using higher doses of etorphine (standardized at 15 mg total dose) with hyaluronidase (4500 IU), to remove the collars. The higher doses of etorphine produced more rapid inductions. Biological data were collected on both occasions. Significant differences in selected measures indicative of stress, including lactic dehydrogenase and aspartate transaminase, were seen between immobilizations. Comparisons were made of selected health measures between samples collected in the early winter and late winter/early spring season. Significant differences were seen with total protein, albumin, urea nitrogen, creatinine, calcium, magnesium, inorganic phosphorus, chloride, and alanine transaminase.

s) Kock,R.A., Morkel,P., and Kock,M.D., 1993. Current immobilization procedures used in elephants. In: Fowler,M.E. (Editor), Zoo and Wild Animal Medicine Current Therapy 3. W.B. Saunders Company, Philadelphia, PA, USA pp. 436-441

t) Raath,J.P., 1993. Chemical capture of the African elephant. In: The Capture and care manual : capture, care, accommodation and transportation of wild African animals. Pretoria : Wildlife Decision Support Services : South African Veterinary  Foundation, Pretoria pp. 484-511

u) Appayya,M.K. and Khadri,S.S.M.S., 1992. Chemical capture of wild elephants and their translocation carried out in Karnataka state. In: Silas,E.G., Nair,M.K., and Nirmalan,G. (Editors), The Asian Elephant: Ecology, Biology, Diseases, Conservation and Management (Proceedings of the National Symposium on the Asian Elephant held at the Kerala Agricultural University, Trichur, India, January 1989). Kerala Agricultural University, Trichur, India pp. 107-112

v) Morton,D.J. and Kock,M.D. 1991. Stability of hyaluronidase in solution with etorphine and xylazine. J.Zoo and Wildlife Medicine 22:(3):345-347  Abstract: During capture of free-living wildlife, stress is potentially the greatest problem encountered. For this reason, reduction in induction time during immobilization is of paramount importance. Hyaluronidase reduces induction times, although no reports have assessed stability of the enzyme in drug mixtures used for chemical capture. This report presents information on the stability of hyaluronidase in combination with etorphine and xylazine, one of the most common drug mixtures used in chemical immobilization of wildlife. Hyaluronidase activity remains high for at least 48 hr, provided storage temperatures can be maintained at less than or equal to 30º C. Storage at greater than or equal to 40ºC is associated with rapid loss of enzyme activity in the mixture.

w) Welsch,B., Jacobson,E.R., Kollias,G.V., Kramer,L., Gardner,H., and Page,C.D. 1989. Tusk extraction in the African elephant (Loxodonta africana). Journal of Zoo and Wildlife Medicine 20:(4):446-453  Abstract: Unilateral dentoalveolar abscesses and/or tusk fractures were identified and tusk extractions performed in seven 3.5-21-yr-old African elephants (Loxodonta africana) of both sexes weighing 650-3,000 kg.  Following immobilization with etorphine hydrochloride or carfentanil citrate, six of seven elephants were intubated and maintained on a 1-1.5% halothane in oxygen mixture; one elephant was maintained in lateral recumbency by multiple i.v. injections of etorphine.  All elephants were positioned with the affected tusk up.  For one elephant, two surgical procedures were required to remove the tusk.  In six of seven elephants, the tusks were sectioned transversely and the tusk wall thinned by enlarging the pulp cavity with carbide burs.  In those tusks with remaining pulp, the pulp was removed with stainless steel rods and hooks.  Next, the tusk was sectioned longitudinally into three or four segments using a wood saw within the pulp chamber.  bone gouges, osteotomes, and a mallet were used to free the outer epithelial and alveolar attachments from the tusk.  Starting with the smallest segment, the sections were removed using long screwdriver-shaped stainless steel rods.  The alveolar chamber was then periodically flushed postsurgically with a dilute organic iodine solution.  For six of seven elephants, complete granulation of the alveolar chamber was evident by 4 mo postsurgery; the seventh elephant showed partial healing with granulation tissue at 2 mo following surgery.

x) Heard,D.J., Kollias,G.V., Webb,A.I., Jacobson,E.R., and Brock,K.A. 1988.  Use of halothane to maintain anesthesia induced with etorphine in juvenile African elephants.  Journal of the American Veterinary Medical Association 193:254-256  Excerpts: Sixteen 3- to 5-year-old African elephants were anesthetized one or more times for a total of 27 diagnostic and surgical procedures.  Xylazine (0.1 ± 0.04 mg/kg of body weight, mean ± SD) and ketamine (0.6 ± 0.13 mg/kg) administered IM induced good chemical restraint in standing juvenile elephants during a 45-minute transport period before administration of general anesthesia.  After IM or IV administration of etorphine (1.9 ± 0.56 micrograms/kg), the mean time to lateral recumbency was 20 ± 6.6 and 3 ± 0.0 minutes, respectively.  The mean heart rate, systolic blood pressure, and respiration rate during all procedures was 50 ± 12 beats/min, 106 ± 19 mm of Hg, and 10 ± 3 breaths/min, respectively. 

Cardiac arrhythmias were detected during 2 procedures.  In one elephant paroxysmal ventricular tachycardia was detected and the procedure terminated when the arrhythmia failed to stabilize after multiple doses of lidocaine (1 mg/kg, IV).  In another elephant, second degree atrioventricular block returned to normal sinus rhythm after IV administration of atropine (0.04 mg/kg).

In one elephant, low mean blood pressure (54 mm of Hg) responded to reduction in halothane (vaporizer setting 1 to 0.75%) and slow infusion of dobutamine HCl ((250 mg/1,000 ml) given to effect. The systolic blood pressure increased to 90 mm of Hg and remained high with a continuous infusion of dobutamine (5 µg/kg/min).

Immediately after induction in another elephant, profound respiratory depression (< 1 breath / minute) and palpably weak arterial pulse were identified.  Intravenous administration of diprenorphine at half the recommended reversal dose resulted in improvement of respiration and palpable arterial pulse, without the elephant developing signs of complete anesthetic reversal.  

Alterations in systolic blood pressure, ear flapping, and trunk muscle tone were useful for monitoring depth of anesthesia.  Results indicated that halothane in oxygen was effective for maintenance of surgical anesthesia in juvenile African elephants after induction with etorphine.  in performing major invasive surgical procedures in African elephants. Note: A correction appeared in a later volume 193(6): p.721.

y) Jacobson,E.R., Heard,D.J., Caligiuri,R., and Kollias,G.V.  1987. Physiologic effects of etorphine and carfentanil in African elephants. Proc.1st.Intl.Conf.Zool.Avian Med. Pages: 525-527 Abstract: (Full text): The effects of etorphine hydrochloride and carfentanil citrate on blood pressure, heart rate, respiration and body temperature were determined in a group of captive African elephants (Loxodonta africana).  Fourteen African elephants, weighing 450 kg to 4000 kg, divided into 2 groups of 6 and 8 elephants each, received either etorphine hydrochloride (2.9 ± 0.7 µg/kg of body weight; mean ± SD) or carfentanil citrate (2.0 ± 0.2 µg/kg of body weight) respectively. The mean time for lateral recumbency in elephants which received etorphine was 31 ± 9.1 minutes while the mean time for lateral recumbency in elephants which received carfentanil was 10.3 ± 4.1 minutes.  Following immobilization, a 18 gauge catheter was inserted into an auricular artery, the catheter connected to a pressure transducer system and systolic, diastolic, and mean arterial pressures were monitored by use of a multichannel oscilloscope.  Systolic, diastolic, mean arterial pressures, heart rate, respiration, and temperature were recorded every 5 minutes over a 45 to 60 minute period.  Elephants were maintained in lateral recumbency over the period of monitoring by intravenous injections of either etorphine or carfentanil. 

Following immobilization with etorphine, mean physiological values for elephants were: systolic pressure, 229 ± 33 mm Hg; diastolic pressure, 141 ± 30 mm Hg; mean arterial pressure, 177 ± 30 mm Hg; heart rate 64 ± 10 beats/minute; respiratory rate 10 ± 4 breaths/minute; body temperature, 97 ± 2°F.  Mean physiological values at the final time period of monitoring prior to antagonism were: systolic pressure, 217 ± 40 mm Hg; diastolic pressure, 147 ± 36 mm Hg; mean arterial pressure, 176 ± 38mm Hg; heart rate 77 ± 13 beats/minute; respiratory rate 12 ± 1 breaths/minute; body temperature, 98 ± 2°F.  Immediately following the last recording, all 8 elephants received the experimental opioid antagonist, nalmefene hydrochloride, administered at 38 ± 11 µg/kg of body weight given both subcutaneously and intravenously.  The mean standing time following administration of nalmefene was 1.4 ± 0.7 minutes.

Immediately following immobilization with carfentanil, mean physiological values for elephants were: systolic pressure, 232 ± 28 mm Hg; diastolic pressure, 148 ± 14 mm Hg; mean arterial pressure, 183 ± 24 mm Hg; heart rate 57 ± 11 beats/minute; respiratory rate 11 ± 3 breaths/minute; body temperature, 99 ± 1°F.  Mean physiological values at the final time period of monitoring prior to antagonism were: systolic pressure, 224 ± 29 mm Hg; diastolic pressure, 146 ± 13 mm Hg; mean arterial pressure, 179 ± 18mm Hg; heart rate 65 ± 11 beats/minute; respiratory rate 12 ± 1 breaths/minute; body temperature, 99 ± 1°F. Immediately following the last recording, all 6 elephants received the opioid antagonist, nalmefene hydrochloride administered at 62 ± 17 µg/kg of body weight given both subcutaneously and intravenously.  The mean standing time following administration of nalmefene was 2.6 ± 1.6  minutes.

The results of this study indicated that both etorphine and carfentanil resulted in high blood pressure over the duration of the period of monitoring.  Based upon these findings, both etorphine hydrochloride and carfentanil citrate are not recommended as the primary agent

z) Jacobson,E.R., Chen,C.-L., Gronwall,R., and Tiller,A. 1986. Serum concentrations of etorphine in juvenile African elephants. Journal of the American Veterinary Medical Association 189:(9):1079-1081  Abstract: Eleven juvenile African elephants were given etorphine hydrochloride (2.19 + 0.11 micrograms/kg body weight, mean +SD) as a single IM injection; 3 elephants were given additional etorphine (0.42+0.09) IV.  After immobilization, each elephant was maintained in lateral recumbency by administration of a 0.5% halothane/oxygen mixture or by administration of multiple IV injections of etorphine.  At postinjection hours 0.25 and 0.5 and at 30-minute intervals thereafter, blood samples were collected via an auricular artery, and serum concentrations of etorphine were determined by use of radioimmunoassay.  The highest mean serum concentration of etorphine in 6 elephants given a single IM injection and subsequently maintained on halothane and oxygen was 1.62+0.97 ng/ml at postinjection hours 0.5; thereafter, the mean serum concentration decreased steadily.  In 4 elephants maintained in lateral recumbency with multiple IV administrations of etorphine, a correlation was not found between the time to develop initial signs of arousal and serum concentrations of etorphine before arousal.  After administration of the initial immobilizing dose of etorphine, the interval between successive IV administrations of etorphine decreased.

aa) Schmidt,M.J., 1986. Proboscidea (Elephants). In: Fowler,M.E. (Editor), Zoo and wild animal medicine. W.B. Saunders, Philadelphia,PA, USA pp. 884-923

bb) Kock,N., Kock,M., Arif,A., and Wahid,M.N.S.A.  1984. Immobilization techniques and complications associated with a bull Indian elephant (Elephas maximus indicus) during musth. Proc.Am.Assoc.Zoo Vet. Pages: 68-74

cc) Bongso,T.A. and Perera,B.M.A.O. 1978. Observations on the use of etorphine alone and in combination with acepromazine maleate for immobilization of aggressive Asian elephants (Elephas maximus). Veterinary Record 102:(15):339-340

dd) Jainudeen,M.R., Bongso,T.A., and Perera,B.M.O.A. 1971. Immobilisation of aggressive working elephants (Elephas maximus). Veterinary Record 89:(26):686-688  
Abstract: The capture of aggressive working elephants, Elephas maximus, by the drug immobilisation technique is described. Doses of 5 mg to 8 mg etorphine hydrochloride alone, satisfactorily immobilised four adult elephants.  Cyprenorphine hydrochloride reversed the immobilising effects almost immediately and completely.  Recovery was uncomplicated.  The value of this method of capture is discussed in relation to aggressive working elephant.

See also:

Hoare,R. 1999. Reducing drug immobilization time in the field immobilization of elephants. Pachyderm 27:(Jan-Dec):49-54

Elkan,P.W., Planton,H.P., Powell,J.A., Haigh,J.A., and Karesh,W.B. 1998. Chemical immobilization of African elephant in lowland forest, southwestern Cameroon. Pachyderm 25:(Jan-July):32-37

Singh,L.A.K., Nayak,B.N., and Acharjya,S.K. 1996. Chemical capture of a problem-elephant in Bolangir, Orissa. Indian Forester. Special issue: wildlife management. 122:(10):955-960  
Abstract: A detailed account is given of the method used to capture an elephant which had been regularly (over 18 yr) entering villages in the Bolangir and Padampur areas of NW Orissa, and causing damage to buildings, eating stored grains and injuring humans. Some 45 people took part in the capture operation which involved the use of darts containing Immobilon (etorphine hydrochloride and acepromazine maleate) to the animal, and of (diprenorphine hydrochloride) for revival. The human antidote for (Narcan) was kept on hand. The communication system, the operational strategies used, and then care and revival processes adopted for the animal are described. It is thought that the animal (with a female) had originally been in the care of a mahout who was taken into custody for some crime so that the animals were abandoned. The female appeared to have been accepted back into the wild, while the male continued to follow the routes used by the mahout. The purpose of capture was to control or translocate the animal.

Dunlop,C.I., Hodgson,D.S., Cambre,R.C., Kenny,D.E., and Martin,H.D. 1994. Cardiopulmonary effects of three prolonged periods of isoflurane anesthesia in an adult elephant. Journal of the American Veterinary Medical Association 205:(10):1439-1444  
Abstract: An adult 3500-kg female African elephant (Loxodonta africana) was anaesthetized 3 times for treatment of subcutaneous fistulas over the lateral aspect of each cubitus (anaesthesia 1 and 2) and for repair of a fractured tusk (anaesthesia 3). Lateral recumbency and anaesthesia were achieved with etorphine (anaesthesia 1 and 2) or etorphine and azaperone (anaesthesia 3). The trachea was intubated and anaesthesia was maintained by isoflurane and oxygen delivered through 2 standard large animal anaesthesia machines joined in parallel. The range of total recumbency time was 2.4 to 3.3 h. Breathing and heart rates, systemic arterial pressure, rectal temperature, PaO2, pH and end-tidal gases were monitored. After administration of etorphine, measurements were made while the elephant was recumbent and breathing air, then every 5 min (cardiovascular) or 15 min (blood gases) after the start of administration of isoflurane and oxygen. Tachycardia and hypertension were detected after administration of etorphine, but heart rate and systemic arterial pressure decreased to within normal ranges after administration of isoflurane and oxygen. The elephant remained well oxygenated while anaesthetized and breathing a high oxygen mixture. The elephant had an uneventful recovery from each anaesthesia.

Still,J. 1993. Etorphine-azaperone anaesthesia in an African elephant (Loxodonta africana). Journal of Veterinary Anaesthesia 20:54-55

Johnsingh,A.J.T., Joshua,J., Ravi,C., Ashraf,N.V.K., Krishnamurthy,V., Khati,D.V.S., and Chellam,R. 1993. Etorphine and acepromazine combination for immobilising wild Indian elephants (Elephas maximus). Journal of the Bombay Natural History Society 90:(2):45-49

Lahiri-Choudhury,D.K., 1992. Translocation of wild elephants. In: Silas,E.G., Nair,M.K., and Nirmalan,G. (Editors), The Asian Elephant: Ecology, Biology, Diseases, Conservation and Management (Proceedings of the National Symposium on the Asian Elephant held at the Kerala Agricultural University, Trichur, India, January 1989). Kerala Agricultural University, Trichur, India pp. 91-106

Ashraf,N.V.K., Johnsingh,A.J.T., Panwar,H.S., Sale,J.B., Joshua,J., Ravi,C., and Krishnamurth,V.  1991. Chemical immobilization of wild Asian elephants: pharmacological, biological and ecological considerations. International Seminar on Veterinary Medicine in Wild and Captive Animals, Nov. 8-10, Bangalore, India. Pages: 21

Jacobson,E.R.  1988. Chemical restraint and anesthesia of elephants. Proc.Ann.Elephant Workshop 9. Pages: 112-119

Mihm,F.G., Machado,C., and Snyder,R. 1988. Pulse oximetry and end-tidal CO2 monitoring of an adult Asian elephant. Journal of Zoo Animal Medicine 19:106-109  
Abstract: The adequacy of ventilation during etorphine anesthesia of a 20-yr-old Asian (3050 kg) elephant (Elephas maximus) was monitored with a pulse oximeter to measure arterial hemoglobin oxygen saturation (SaO2) and a CO2 analyzer to measure end-tidal CO2 concentrations (PetCO2).  Immediately after the first anesthetic induction (8 mg etorphine IV), SaO2 values of 45% were noted while the animal was breathing room air at a rate of 6/min.  The SaO2 readings increased to 93% 15 min after administration of 5 liters/min of oxygen via the trunk.  Seven arterial blood gas samples obtained during two anesthetics, and once while unanesthetized, provided PaO 2and PaCO2 values which compared favorably with SaO2 and PetCO2.  In the anesthetized animal, PaO2 ranged between 31 and 70 mmHg while SaO2 values were 70-95%.  At the same time, measurements of PaCO2 ranged from 42 to 57 mmHg while values of PetCO2 ranged from 35 to 57 mmHg.  Pulse oximetry and end-tidal CO2monitoring are easy to apply and should increase the safety of anesthesia for these animals. Note: Atropine (120 mg) IV was given after induction. Duration of surgery was 60 minutes. Diprenorphine (16 mg) was given IV for reversal and the elephant stood in 9 minutes.

Heard,D.J., Jacobson,E.R., and Brock,K.A. 1986. Effects of oxygen supplementation on blood gas values in chemically restrained juvenile African elephants. Journal of the American Veterinary Medical Association 189:(9):1071-1074  Abstract: Arterial oxygen and carbon dioxide tensions were determined in sedated immature African elephants and in elephants immobilized with etorphine hydrochloride or with an etorphine-ketamine combination.  For manipulative and surgical procedures, the Hudson demand value was used for oxygen supplementation during 6 procedures, and insufflation was used during 2 procedures.  The Hudson demand value was more effective than insufflation in sustaining adequate arterial oxygenation.

Lateur,N. and Stolk,P.  1986. Repeated general anesthesia in a male Indian elephant. Proc.Am.Assoc.Zoo Vet. Pages: 128-131

Hattingh,J. 1984. Effects of etorphine and succinyldicholine on blood composition in elephant and buffalo. South African Journal of Zoology 19:286-290

Tamas,P.M. and Geiser,D.R. 1983. Etorphine analgesia supplemented by halothane anesthesia in an adult African elephant. Journal of the American Veterinary Medical Association 183:(11):1312-1314

Fowler,M.E. 1981. Problems with immobilizing and anesthetizing elephants. Proceedings of the American Association of Zoo Veterinarians 87-91

Jarofke,D. 1981. Etorphine anesthesia in the elephant. Journal of Zoo Animal Medicine 12: 93-95

von Richter,W., Drager,N., Patterson,L., and Sommerlatte,M. 1978. Observations on the immobilization and marking of African elephants (Loxodonta africana) in Botswana. Akademie-Verlag 14:185-191  Abstract: 58 elephants were successfully immobilized in their natural environment in the Chobe Nation Park and on privately owned farms in Botswana using a drug mixture of etorphine (M99 Reckitt) and acetylpromazine.  The specific antidote cyprenorphine (M285 Reckitt) was used in most cases to resuscitate the animals.  One known mortality occurred.  For the long term monitoring of social organization and long and short term movements collars manufactured from machine belting and fitted with colour codes or symbols proved most satisfactory. Stamping the tusks near the lip provided a permanent marking although not useful for field observation.  Various other marking techniques were tested but were considered unsatisfactory for long term identification.  Various behavioral aspects associated with the immobilizing of elephants are described and discussed.

Ebedes,H. 1975. The immobilization of adult male and female elephant, Loxodonta africana, with etorphine and observation on the action of diprenorphine. Madogua 9:19-24

Alford,B.T., Burkhart,R.L., and Johnson,W.P. 1974. Etorphine and diprenorphine as immobilizing and reversing agents in captive and free-ranging mammals. Journal of the American Veterinary Medical Association 164:(7):702-705

Fowler,M.E. and Hart,R. 1973. Castration of an Asian elephant, using etorphine anesthesia. Journal of the American Veterinary Medical Association 163:(6):539-543  
Abstract: A 9-year-old Asian elephant was castrated, using etorphine HCl for anesthesia.  The intra-abdominal surgery was completed in 2 stages.  Respiratory and heart rates were normal throughout each surgical procedure.  Normal PaCO2 and PaO2 were maintained without the need of intermittent positive pressure ventilation.

Jainudeen,M.R., Bongso,T.A., and Perera,B.M.O.A. 1971. Immobilisation of aggressive working elephants (Elephas maximus). Veterinary Record 89:(26):686-688  
Abstract: The capture of aggressive working elephants, Elephas maximus, by the drug immobilisation technique is described. Doses of 5 mg to 8 mg etorphine hydrochloride alone, satisfactorily immobilised four adult elephants.  Cyprenorphine hydrochloride reversed the immobilising effects almost immediately and completely.  Recovery was uncomplicated.  The value of this method of capture is discussed in relation to aggressive working elephant.

Gray,C.W. and Nettasinghe,A.P.W. 1970. A preliminary study of immobilization of the Asiatic elephant (Elephas maximus) utilizing etorphine (M-99). Zoologica 55:51-53  
Ref Type: Journal  Language: English  Abstract: A preliminary study of M-99 for the immobilization of the Ceylonese elephant indicates the effective dosage is approximately twice that used in the African elephant, based on comparative body weights.  A dosage rate of 7 to 8 mgs of M-99 was necessary to immobilize the Ceylonese elephant as compared to 5 or 6 mgs of M-99 for African elephants of almost double the weight.

Jainudeen,M.R. 1970. The use of etorphine hydrochloride for restraint of a domesticated elephant (Elephas maximus). Journal of the American Veterinary Medical Association 157:(5):624-626  Abstract: A domestic male Asian elephant (Elephas maximus) in “musth” (aggressive state) was successfully immobilized with 8 mg. of etorphine hydrochloride (M.99).  The clinical signs of immobilization were comparable to those reported in the African elephant (Loxodonta africana).  Cyprenorphine hydrochloride (M.285) reversed the immobilizing effects almost immediately and completely.  Recovery was uncomplicated.

Gandal,C.P. 1968. M-99 usage in African elephant, okapi and blesbok. American Association of Zoo Veterinarians Newsletter 1:

Gray,C.W. 1968. The use of M-99 in wild Asian elephant. American Association of Zoo Veterinarians Newsletter March 25:

Wallach,J.D. and Anderson,J.L. 1968. Oripavine (M.99) combinations and solvents for immobilization of the African elephant. Journal of the American Veterinary Medical Association 153:(7):793-797  Abstract: The oripavine derivative, M.99, alone or in combination with small amounts of tranquilizer, satisfactorily immobilized 21 adult African elephants.  The addition of scopolamine to M.99 solutions in doses high enough to produce a physiologic effect prolonged the recovery period unnecessarily. There was no reduction of the induction period when dimethyl sulfoxide was used as a solvent for M.99 given subcutaneously or by deep intramuscular injections.  Cyprenorphine (M.285) reversed the immobilizing effects of M.99 alone or in combination with small amounts of tranquilizer.

Pienaar,U.d.V., Van Niekerk,J.W., and Young,E. 1966. The use of oripavine hydrochloride (M.99) in the drug immobilization and marking of wild African elephant (Loxodonta africana Blumenbach) in the Kruger national park. Koedoe 9:108-124

Harthoorn,A.M. and Bligh,J. 1965. The use of a new oripavine derivative with potent morphine-like activity for the restraint of hoofed wild animals. Research in Veterinary Science 6:290-299  Abstract: The use of one of a series of oripavine derivatives (No. M.99) for the immobilization and capture of hoofed wild animals is described.  This substance, usually injected in combination with tranquilizer and hyoscine, is suitable for the restraint of all hoofed wild animals on which it has been used. The very low mortality achieved originally with the use of tranquilizer/synthetic morphine/hyoscine mixtures has been maintained, while the speed of reaction has greatly increased. The much smaller bulk of this substance (approximately 0.2 ml compared with 10 ml equivalent of solution formerly needed) has considerably increased the ease of injection through the use of much smaller projectile syringes.  The effect of this oripavine substance may be reversed with nalorphine.