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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, cefazolin sodium occurs as a practically odorless or having a faint odor, white to off-white, crystalline powder or lyophilized solid. It is freely soluble in water and very slightly soluble in alcohol. Each gram of the injection contains 2 mEq of sodium. After reconstitution, the solution for injection has a pH of 4.5 – 6 and has a light yellow to yellow color. May also be known as cephazolin sodium in the U.K. and other countries.
Storage/Stability/Compatibility – Cefazolin sodium powder for injection and solutions for injection should be protected from light. The powder for injection should be stored at room temperature (15-30°C); avoid temperatures above 40°C. The frozen solution for injection should be stored at temperatures no higher than -20°C.
After reconstitution, the solution is stable for 24 hours when kept at room temperature and 96 hours if refrigerated. If after reconstitution, the solution is immediately frozen in the original container, the preparation is stable for at least 12 weeks when stored at -20°C.
The following drugs or solutions are reportedly compatible with cephapirin: Amino acids 4.25%/dextrose 25%, D5W in Ringer’s, D5W in Lactated Ringer’s, D5W in sodium chloride 0.2% – 0.9%, D5W, D10W, Ringer’s Injection, Lactated Ringer’s Injection, normal saline, metronidazole, verapamil HCl and vitamin B-complex.
The following drugs or solutions are reportedly incompatible or only compatible in specific situations with cefazolin: amikacin sulfate, amobarbital sodium, ascorbic acid injection, bleomycin sulfate, calcium chloride/gluconate, cimetidine HCl, erythromycin gluceptate, kanamycin sulfate, lidocaine HCl, oxytetracycline HCl, pentobarbital sodium, polymyxin B sulfate, tetracycline HCl and vitamin B-complex with C injection.
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, cefazolin exhibits activity against the bacteria usually covered by this class. Because MIC’s occasionally differ for cefazolin when compared to either cephalothin/cephapirin, some clinical microbiologists recommend also testing bacterial susceptibilities for this antibiotic. For more specific information, refer to the monograph, Cephalosporins, General Information.
Uses/Indications – In the United States, there are no cefazolin products approved for veterinary species, but it has been used clinically in several species when an short-acting injectable first generation cephalosporin is indicated.
Pharmacokinetics (specific) – Cefazolin is not appreciably absorbed after oral administration and must be given parenterally to achieve therapeutic serum levels. Absorbed drug is excreted unchanged by the kidneys into the urine. Elimination half-lives may be significantly prolonged in patients with severely diminished renal function. Pharmacokinetic parameters for dogs and horses follow:
In dogs, peak levels occur in about 30 minutes after IM administration. The apparent volume of distribution at steady state is 700 ml/kg, total body clearance of 10.4 ml/min/kg with a serum elimination half-life of 48 minutes. Approximately 64% of the clearance can be attributed to renal tubular secretion. The drug is approximately 16-28% bound to plasma proteins in dogs.
In horses, the apparent volume of distribution at steady state is 190 ml/kg, total body clearance of 5.51 ml/min/kg with a serum elimination half-life of 38 minutes when given IV and 84 minutes after IM injection (gluteal muscles). Cefazolin is about 4-8% bound to equine plasma proteins. Because of the significant tubular secretion of the drug, it would be expected that probenecid administration would alter the kinetics of cefazolin. One study performed in horses (Donecker, Sams, and Ashcroft 1986), did not show any effect, but the author’s concluded that the dosage of probenecid may have been sub-therapeutic in this species.
In calves, the volume of distribution is 165 ml/kg, and had a terminal elimination half-life of 49-99 minutes after IM administration.
For susceptible infections:
a) Respiratory tract: 11 mg/kg IV or IM q12h (Beech 1987a)
b) 11 mg/kg IV or IM qid (Robinson 1987)
c) Foals: 20 mg/kg IV q8-12h (Caprile and Short 1987)
Dosage Forms/Preparations/FDA Approval Status –
Veterinary-Approved Products: None
Cefazolin Sodium Powder for Injection 250 mg (of cefazolin), 500 mg, 1, 5, 10, & 20g; Ancef® (SKF); Kefzol® (Lilly); Zolicef® (Apothecon);Cefazolin Sodium® (Apothecon). (Rx)
Cefazolin Sodium for Injection (IV infusion) 500 mg in 5% Dextrose in Water (of cefazolin), 1 g in 5% Dextrose in Water, 1 g in 10 ml vials; Ancef® (SKB), Kefzol® (Lilly); (Rx)