Clinical pharmacology of ceftriaxone in patients with neoplastic disease

Pharmacological studies of ceftriaxone, a new semisynthetic cephalosporin, were conducted in 35 cancer patients. This antibiotic was administered in a variety of doses and schedules with no observed toxicity. Intramuscular administration of 500 mg of ceftriaxone to seven patients produced mean peak serum concentrations of 32.9 mug/ml 2.0 h after administration. The terminal serum half-life was 10.9 h. Intravenous infusion of 500 mg of ceftriaxone over 5 min to the same group of seven patients produced a mean peak concentration of the drug in serum of 83 mug/ml at the end of administration which decreased to 16.8 mug/ml at 8 h. A dose of 1 g of ceftriaxone given in identical fashion to the same group of seven patients produced mean peak concentrations in serum of 130 mug/ml at the end of administration and 17.3 mug/ml at 12 h. The mean percentages of drug recovered in urine 12 h after single intravenous doses of 500 mg and 1 g were 30 and 20%, respectively. A 1-g dose of ceftriaxone was administered every 8 h to 10 patients, and a 2-g dose was administered every 12 hours to 9 patients. Drug concentrations in serum were measured for each patient after drug administration on day 1, day 3 or 4, and day 7 or 8. The 1-g dose produced an observed mean peak concentration of 154 mug/ml and a mean terminal-phase half-life of 5.6 h on day 3 or 4. The 2-g dose produced a mean peak concentration in serum of 262 mug/ml and a terminal-phase serum half-life of 6.3 h on day 3 or 4. Continuous infusion studies were performed in nine neutropenic patients for up to 8 days by using a loading dose of 1 g over 30 min, followed by 2 g every 8 h. Mean concentrations in serum were maintained at about 135 mug/ml during the infusion period.