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For general information on the cephalosporins including adverse effects, contraindications, overdosage, drug interactions, and monitoring parameters, refer to the monograph: Cephalosporins, General Information.
Chemistry – An injectable semi-synthetic cephalosporin antibiotic, cephapirin sodium occurs as a white to off-white, crystalline powder having a faint odor. It is very soluble in water and slightly soluble in alcohol. Each gram of the injection contains 2.36 mEq of sodium. After reconstitution the solution for injection has a pH of 6.5-8.5. May also be known as cefapirin sodium in the U.K. and other countries.
Storage/Stability/Compatibility – The sterile powder for injection and reconstitution should be stored at room temperature and is stable for 24 months in dry state. After reconstituting with sterile water for injection in concentrations of 50 – 400 mg/ml, cephapirin is stable for 12 hours at room temperature. After reconstituting with bacteriostatic water for injection in concentrations of 250 – 400 mg/ml, cephapirin is stable for 48 hours at room temperature. After reconstituting with sodium chloride 0.9% injection or dextrose 5% in water in concentrations of 20 – 100 mg/ml, cephapirin is stable for 24 hours at room temperature. All of the above solutions are stable for 10 days when stored at 4°C (refrigeration) and may be stable longer when solutions are frozen. Solutions may become yellow, but this does not indicate any loss of potency.
Cephapirin mastitis tubes should be stored at room temperature (15-30°C); avoid excessive heat.
The following drugs or solutions are reportedly compatible with cephapirin: D5W in Ringer’s, D5W in Lactated Ringer’s, D5W in sodium chloride 0.2% – 0.9%, D5W, D10W, D20W, Ringer’s Injection, Lactated Ringer’s Injection, normal saline, bleomycin sulfate, calcium chloride/gluconate, chloramphenicol sodium succinate, diphenhydramine HCl, ergonovine maleate, heparin sodium, hydrocortisone sodium phosphate/succinate, metaraminol bitartrate, oxacillin sodium, penicillin G potassium/sodium, phenobarbital sodium, phytonadione, potassium chloride, sodium bicarbonate, succinylcholine chloride, verapamil HCl, vitamin B-complex with C and warfarin sodium.
The following drugs or solutions are reportedly incompatible or only compatible in specific situations with cephapirin: Mannitol 20%, amikacin sulfate, aminophylline, ascorbic acid injection, epinephrine HCl, erythromycin gluceptate, gentamicin sulfate, kanamycin sulfate, nitrofurantoin sodium, norepinephrine bitartrate, oxytetracycline HCl, phenytoin sodium, tetracycline HCl, and thiopental sodium.
Compatibility is dependent upon factors such as pH, concentration, temperature and diluents used. It is suggested to consult specialized references for more specific information (e.g., Handbook on Injectable Drugs by Trissel; see bibliography).
Pharmacology/Spectrum of Activity – A first generation cephalosporin, cephapirin exhibits activity against the bacteria usually covered by this class. A cephalothin disk is usually used to determine bacterial susceptibility to this antibiotic when using the Kirby-Bauer method. Refer to the monograph: Cephalosporins, General Information for more specific information.
Uses/Indications – In the United States, there are no parenterally administered cephapirin products approved for veterinary species, but it has been used clinically in several species when a relatively short-acting injectable first generation cephalosporin is indicated.
An intramammary cephapirin sodium product (Cefa-Lak®—Fort Dodge) is approved for use in the treatment of mastitis in lactating dairy cows and cephapirin benzathine (Cefa-Dri®—Fort Dodge) is approved in dry cows.
Pharmacokinetics (specific) – Cephapirin is not appreciably absorbed after oral administration. In horses, the bioavailability is about 95% after IM injection. The apparent volumes of distribution have been reported as 0.32 L/kg in dogs, 0.335 – 0.399 L/kg in cattle and 0.17 – 0.188 L/kg in horses. The total body clearance of cephapirin is 8.9 ml/min/kg in dogs, 12.66 ml/min/kg in cattle and about 7.8 – 10 ml/min/kg in horses. Serum elimination half-life is about 25 minutes in dogs, 64 – 70 minutes in cattle and 25-55 minutes in horses. Probenecid has been demonstrated to reduce the renal clearance of the drug.
For susceptible infections:
a) 20 mg/kg IM q8h or q12h if administered with probenecid (50 mg/kg intragastrically). (Juzwiak et al. 1989)
b) Foals: 20 – 30 mg/kg IV q6h (Caprile and Short 1987)
c) 20 mg/kg IM q8h (Brumbaugh 1987)
Dosage Forms/Preparations/FDA Approval Status/Withholding Times –
Cephapirin Sodium Mastitis Tube; 200 mg cephapirin per 10 ml tube; Cefa-Lak® (Fort Dodge); (OTC) Approved for use in lactating dairy cattle. Milk withdrawal = 96 hours; Slaughter withdrawal = 4 days.
Cephapirin Benzathine Mastitis Tube; 300 mg cephapirin per 10 ml tube; Cefa-Dri® (Fort Dodge); (OTC) Approved for use in dry dairy cattle. Milk withdrawal = 72 hours after calving and must not be administered within 30 days of calving; Slaughter withdrawal = 42 days.
Cephapirin Sodium Powder for Injection 500 mg, 1 g, 2 g, 4 g, 20 g; Cefadyl® (Apothecon);Cephapirin Sodium® (Lyphomed); , generic; (Rx)