The pharmacokinetics of ceftizoxime, a new beta-lactam antibiotic, were studied in normal, male volunteers and compared with the pharmacokinetics of cefamandole. After administration of 500 mg intramuscularly, ceftizoxime produced a peak level of 13.7 +/- 1 microgram/ml, compared with 13.2 +/- 1.6 microgram/ml for cefamandole. At 4 h, the serum level of ceftizoxime was 4.8 micrograms/ml, and that of cefamandole was 1.9 microgram/ml. At 8 h, ceftizoxime was still detected at 0.73 microgram/ml, whereas cefamandole was not. The half-life of ceftizoxime after intramuscular administration was 1.7 h, compared with 1 h for cefamandole. Serum levels of ceftizoxime and cefamandole after 1 g infused over 30 min were 84 and 88 micrograms/ml, respectively. At 5 h cefamandole was not detectable, whereas ceftizoxime had a serum level of 4.5 micrograms/ml and, at 7 h, 2.1 micrograms/ml. The half-life of ceftizoxime was 1.9 h, compared with 0.78 h for cefamandole. Urinary recovery of ceftizoxime after intramuscular and intravenous administration was 70 and 80%, respectively, compared with 78 and 73% for cefamandole.