Cefazolin 1000 mg · Dry-powder injectables

Cefazolin is an antibacterial drug [see Microbiology (12.4)].

Studies have shown that following intravenous administration of cefazolin to normal volunteers, mean serum concentrations peaked at approximately 185 mcg/mL and were approximately 4 mcg/mL at 8 hours for a 1 gram dose.

In a study of constant intravenous infusion with dosages of 3.5 mg/kg for 1 hour (approximately 250 mg) and 1.5 mg/kg the next 2 hours (approximately 100 mg) in healthy volunteers, cefazolin serum concentrations at the third hour were approximately 28 mcg/mL.

Plasma pharmacokinetic parameters of cefazolin in healthy volunteers (N=12) following a single 15-minute IV infusion of 2 grams of Cefazolin for Injection are summarized in Table 4.

*Tmax reported as median (range) — N= number of subjects observed; Cmax = maximum plasma concentration; Tmax = time to maximum plasma concentration; AUC0-inf = area under the plasma concentration-time curve extrapolated to infinity; t1/2 = apparent plasma terminal elimination half-life; CL = total clearance; Vz = volume of distribution

Studies in patients hospitalized with infections indicate that cefazolin produces mean peak serum concentrations approximately equivalent to those seen in normal volunteers.

Distribution — Bile concentrations in patients without obstructive biliary disease can reach or exceed serum concentrations by up to five times; however, in patients with obstructive biliary disease, bile concentrations of cefazolin are considerably lower than serum concentrations (less than 1 mcg/mL).

In synovial fluid, the cefazolin concentration becomes comparable to that reached in serum at about 4 hours after drug administration.

Studies of cord blood show prompt transfer of cefazolin across the placenta. Cefazolin is present in very low concentrations in the milk of nursing mothers.

Elimination — The serum half-life for cefazolin is approximately 1.8 hours following IV administration.

Excretion — Cefazolin is excreted unchanged in the urine. In the first 6 hours approximately 60% of the drug is excreted in the urine and this increases to 70% to 80% within 24 hours.