DOSAGE AND ADMINISTRATION Usual Adult Dosage Type of Infection Dose Frequency Moderate to severe infections 500 mg to 1 gram every 6 to 8 hours Mild infections caused by susceptible gram-positive cocci 250 mg to 500 mg every 8 hours Acute, uncomplicated urinary tract infections 1 gram every 12 hours Pneumococcal pneumonia 500 mg every 12 hours Severe, life-threatening infections (e.g., endocarditis, septicemia) 1 gram to 1.5 grams every 6 hours * In rare instances, doses of up to 12 grams of cefazolin for injection per day have been used. Perioperative Prophylactic Use To prevent postoperative infection in contaminated or potentially contaminated surgery, recommended doses are: a. 1 gram intravenous or intramuscular administered 1/2 hour to 1 hour prior to the start of surgery. b. For lengthy operative procedures (e.g., 2 hours or more), 500 mg to 1 gram intravenous or intramuscular during surgery (administration modified depending on the duration of the operative procedure). c. 500 mg to 1 gram intravenous or intramuscular every 6 to 8 hours for 24 hours postoperatively. It is important that (1) the preoperative dose be given just (1/2 to 1 hour) prior to the start of surgery so that adequate antibiotic levels are present in the serum and tissues at the time of initial surgical incision; and (2) cefazolin for injection be administered, if necessary, at appropriate intervals during surgery to provide sufficient levels of the antibiotic at the anticipated moments of greatest exposure to infective organisms. In surgery where the occurrence of infection may be particularly devastating (e.g., open-heart surgery and prosthetic arthroplasty), the prophylactic administration of cefazolin for injection may be continued for 3 to 5 days following the completion of surgery. Dosage Adjustment for Patients with Reduced Renal Function Cefazolin for injection may be used in patients with reduced renal function with the following dosage adjustments: Patients with a creatinine clearance of 55 mL/min. or greater or a serum creatinine of 1.5 mg % or less can be given full doses. Patients with creatinine clearance rates of 35 to 54 mL/min. or serum creatinine of 1.6 to 3 mg% can also be given full doses but dosage should be restricted to at least 8 hour intervals. Patients with creatinine clearance rates of 11 to 34 mL/min. or serum creatinine of 3.1 to 4.5 mg% should be given 1/2 the usual dose every 12 hours. Patients with creatinine clearance rates of 10 mL/min. or less or serum creatinine of 4.6 mg% or greater should be given 1/2 the usual dose every 18 to 24 hours. All reduced dosage recommendations apply after an initial loading dose appropriate to the severity of the infection. Patients undergoing peritoneal dialysis: see CLINICAL PHARMACOLOGY . Pediatric Dosage In pediatric patients, a total daily dosage of 25 to 50 mg per kg (approximately 10 to 20 mg per pound) of body weight, divided into 3 or 4 equal doses, is effective for most mild to moderately severe infections. Total daily dosage may be increased to 100 mg per kg (45 mg per pound) of body weight for severe infections. Since safety for use in premature infants and in neonates has not been established, the use of cefazolin for injection in these patients is not recommended. Pediatric Dosage Guide Weight 25 mg/kg/day Divided into 3 Doses 25 mg/kg/day Divided into 4 Doses lbs kg Approximate Single Dose (mg/every 8 hours) Vol. (mL) Needed with Dilution of 125 mg/mL Approximate Single Dose (mg/ every 6 hours) Vol. (mL) Needed with Dilution of 125 mg/mL 10 4.5 40 mg 0.35 mL 30 mg 0.25 mL 20 9 75 mg 0.6 mL 55 mg 0.45 mL 30 13.6 115 mg 0.9 mL 85 mg 0.7 mL 40 18.1 150 mg 1.2 mL 115 mg 0.9 mL 50 22.7 190 mg 1.5 mL 140 mg 1.1 mL Weight 50 mg/kg/day Divided into 3 Doses 50 mg/kg/day Divided into 4 Doses lbs kg Approximate Single Dose (mg/ every 8 hours) Vol. (mL) Needed with Dilution of 225 mg/mL Approximate Single Dose (mg/ every 6 hours) Vol. (mL) Needed with Dilution of 225 mg/mL 10 4.5 75 mg 0.35 mL 55 mg 0.25 mL 20 9 150 mg 0.7 mL 110 mg 0.5 mL 30 13.6 225 mg 1 mL 170 mg 0.75 mL 40 18.1 300 mg 1.35 mL 225 mg 1 mL 50 22.7 375 mg 1.7 mL 285 mg 1.25 mL In pediatric patients with mild to moderate renal impairment (creatinine clearance of 70 to 40 mL/min.), 60 percent of the normal daily dose given in equally divided doses every 12 hours should be sufficient. In patients with moderate impairment (creatinine clearance of 40 to 20 mL/min.), 25 percent of the normal daily dose given in equally divided doses every 12 hours should be adequate. Pediatric patients with severe renal impairment (creatinine clearance of 20 to 5 mL/min.) may be given 10 percent of the normal daily dose every 24 hours. All dosage recommendations apply after an initial loading dose.