Elephant specific information, if available, is in blue.

For general information on the penicillins, including adverse effects, contraindications, overdosage, drug interactions and monitoring parameters, refer to the monograph: Penicillins, General Information.

Chemistry – An isoxazolyl-penicillin, oxacillin sodium is a semisynthetic penicillinase-re­sistant penicillin. It is available commercially as the monohydrate sodium salt which oc­curs as a fine, white, crystalline powder that is odorless or has a slight odor. It is freely soluble in water and has a pKa of about 2.8. One mg of oxacillin sodium contains not less than 815-950 micrograms of oxacillin. Each gram of the commercially available powder for injection contains 2.8 -3.1 mEq of sodium. Oxacillin sodium may also be known as sodium oxacillin  or methylphenyl isoxazolyl penicillin .

Storage/Stability/Compatibility – Oxacillin sodium capsules, powder for oral solution, and powder for injection should be stored at room temperature (15-30°C) in tight contain­ers. After reconstituting with water, refrigerated and discard any remaining oral solution after 14 days. If kept at room temperature, the oral solution is stable for 3 days.

After reconstituting the sterile powder for injection with sterile water for injection or ster­ile sodium chloride 0.9%, the resultant solution with a concentration of 167 mg/ml is sta­ble for 3 days at room temperature or 7 days if refrigerated. The manufacturer recom­mends using different quantities of diluent depending on whether the drug is to be admin­istered IM, IV directly, or IV (piggyback). Refer to the package insert for specific instruc­tions.

Oxacillin sodium injection is reportedly compatible with the following fluids/drugs: dex­trose 5% & 10% in water, dextrose 5% & 10% in sodium chloride 0.9%, lactated Ringer’s injection, sodium chloride 0.9% amikacin sulfate, cephapirin sodium, choramphenicol sodium succinate, dopamine HCl, potassium chloride, sodium bicarbonate and verapamil.

Oxacillin sodium injection is reportedly incompatible with the following fluids/drugs: oxytetracycline HCl and tetracycline HCl. 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/Uses/Indications – Refer to the Cloxacillin monograph and the Doses section for Oxacillin for more information regarding this drug.

Pharmacokinetics (specific) – Oxacillin sodium is resistant to acid inactivation in the gut, but is only partially absorbed after oral administration. The bioavailability after oral ad­ministration in humans has been reported to range from 30-35%, and, if given with food, both the rate and extent of absorption is decreased. After IM administration, oxacillin is rapidly absorbed and peak levels generally occur within 30 minutes.

The drug is distributed to the lungs, kidneys, bone, bile, pleural fluid, synovial fluid and ascitic fluid. The volume of distribution is reportedly 0.4 L/kg in human adults and 0.3 L/kg in dogs. As with the other penicillins, only minimal amounts are distributed into the CSF, but levels are increased with meningeal inflammation. In humans, approximately 89-94% of the drug is bound to plasma proteins.

Oxacillin is partially metabolized to both active and inactive metabolites. These metabo­lites and the parent compound are rapidly excreted in the urine via both glomerular filtra­tion and tubular secretion mechanisms. A small amount of the drug is also excreted in the feces via biliary elimination. The serum half-life in humans with normal renal function ranges from about 18-48 minutes. In dogs, 20-30 minutes has been reported as the elimi­nation half-life.

Doses –

Horses:

For susceptible infections:

a)   Foals: 20 – 30 mg/kg IV q6-8h (Dose extrapolated from adult horse data; use lower dose or longer interval in premature foals or those less than 7 days old.) (Caprile and Short 1987)

b)   25 – 50 mg/kg IM, IV bid (Robinson 1987)

Client Information – Unless otherwise instructed by the veterinarian, this drug should be given on an empty stomach, at least 1 hour before feeding or 2 hours after. Keep oral solu­tion in the refrigerator and discard any unused suspension after 14 days.

Dosage Forms/Preparations/FDA Approval Status –

Veterinary-Approved Products: None

Human-Approved Products:

Oxacillin Sodium  Capsules 250 mg, 500 mg; Prostaphlin®  (Apothecon) (Rx), Bactocill®  (Beecham); (Rx); generic, (Rx)

Oxacillin Sodium Powder for Oral Solution 250 mg/5 ml in 100 ml bottles; Prostaphlin®  (Apothecon); (Rx)

Oxacillin Sodium Powder for Injection 250 mg vials, 500 mg vials, 1 g, 2 g, & 4 g vials; 1 g & 2 g piggyback vials, 4 g and 10 g bulk vials; Prostaphlin® (Apothecon) (Rx); Bactocill® (S-K Beecham); (Rx); Oxacillin Sodium® (Apothecon) (Rx)