CEPHAPIRIN SODIUM, CEPHAPIRIN BENZATHINE
Chemistry - An injectable semi-synthetic cephalosporin antibiotic, cephapirin sodium occurs as awhite to off-white, crystalline powder having a faint odor. It is very soluble in water and slightlysoluble in alcohol. Each gram of the injection contains 2.36 mEq of sodium. After reconstitution thesolution for injection has a pH of 6.5-8.5. May also be known as cefapirin sodium in the U.K. andother countries.
Storage, Stability, CompatibilityThe sterile powder for injection and reconstitution should bestored at room temperature and is stable for 24 months in dry state. After reconstituting with sterilewater for injection in concentrations of 50 - 400 mg/ml, cephapirin is stable for 12 hours at roomtemperature. 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 sodiumchloride 0.9% injection or dextrose 5% in water in concentrations of 20 - 100 mg/ml, cephapirin isstable for 24 hours at room temperature. All of the above solutions are stable for 10 days whenstored at 4°C (refrigeration) and may be stable longer when solutions are frozen. Solutions maybecome 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 Gpotassium/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 specificsituations with cephapirin: Mannitol 20%, amikacin sulfate, aminophylline, ascorbic acid injection, epinephrine HCl, erythromycin gluceptate, gentamicin sulfate, kanamycin sulfate, nitrofurantoinsodium, norepinephrine bitartrate, oxytetracycline HCl, phenytoin sodium, tetracycline HCl, andthiopental 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 themonograph: Cephalosporins, General Information for more specific information.
Uses, Indications - In the United States, there are no parenterally administered cephapirin productsapproved for veterinary species, but it has been used clinically in several species when a relativelyshort-acting injectable first generation cephalosporin is indicated.
An intramammary cephapirin sodium product (Cefa-Lak®¯Fort Dodge) is approved for use inthe 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 distributionhave been reported as 0.32 L/kg in dogs, 0.335 - 0.399 L/kg in cattle and 0.17 - 0.188 L/kg inhorses. The total body clearance of cephapirin is 8.9 ml/min/kg in dogs, 12.66 ml/min/kg in cattleand 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 therenal clearance of the drug.