Oral absorption and tolerance in man, of a new penem antibiotic, Sch 29428

Pharmacokinetics of the penem CP-65,207 and its separate stereoisomers in humans

CP-65,207 is a new broad-spectrum penem antimicrobial agent that is a 1:1 mixture of two stereoisomers. Five minutes after a 10-min intravenous infusion of 1 g of CP-65,207 to volunteers, mean concentrations in serum were 33 micrograms of the R isomer per ml and 29 micrograms of the S isomer per ml. Following rapid distribution, half-lives of the isomers were 53 and 55 min, respectively. Concentrations in urine exceeded 800 micrograms of each isomer per ml. Recovery of the S isomer in urine (46%) was much greater than recovery of the R isomer (26%). The serum kinetics of the S isomer (volume of distribution, 319 ml/kg; total clearance, 315 ml/min; elimination rate constant, 0.80 h-1 were similar when it was given alone and when it was contained in CP-65,207, demonstrating that the presence of the R isomer has little effect on the serum kinetics of the S isomer. However, when the S isomer was given alone, the urinary recovery of intact S isomer (36%) was substantially lower than that when it was given with the R isomer as CP-65,207 (57%). Administration of the S isomer alone did not produce the unpleasant sulfurous odor in urine that was observed following administration of CP-65,207. Oral doses of a prodrug, which contained 1 g of CP-65,207, produced peak concentrations in serum of 1.6 micrograms of the R isomer per ml and 1.8 micrograms of the S isomer per ml. Approximately 36% of the S-isomer component was absorbed, and 20% of this isomer was recovered in urine. A 1-g oral dose of the prodrug of the single S isomer provides concentrations in serum above 1.0 microgram/ml (the MIC for 90% of over 1,000 hospital pathogens) for 3.5 h, suggesting that the drug given orally will prove to be efficacious against many infections.

Discovery and development of new antimicrobial agents

The unprecedented growth in the number of new antibiotics over the past two decades has been the result of extensive research efforts that have exploited the growing body of knowledge describing the interactions of antibiotics with their targets in bacterial cells. Information gained from one class of antimicrobial agents has often been used to advance the development of other classes. In the case of beta-lactams, information on structure-activity relationships gleaned from penicillins and cephalosporins was rapidly applied to the cephamycins, monobactams, penems, and carbapenems in order to discover broad-spectrum agents with markedly improved potency. These efforts have led to the introduction of many new antibiotics that demonstrate outstanding clinical efficacy and improved pharmacokinetics in humans. The current review discusses those factors that have influenced the rapid proliferation of new antimicrobial agents, including the discovery of new lead structures from natural products and the impact of bacterial resistance development in the clinical setting. The development process for a new antibiotic is discussed in detail, from the stage of early safety testing in animals through phase I, II, and III clinical trials.

Comparative in vitro antibacterial activity of Sch 34343, a novel penem antibiotic

Using agar and broth dilutions, Sch 34343 was found to be highly active against gram-positive and gram-negative aerobic, facultatively anaerobic, and anaerobic bacteria, with the exceptions of enterococci, methicillin-resistant staphylococci, and Pseudomonas spp., which were resistant. Comparisons were made with imipenem, cefuroxime, cefotaxime, gentamicin, clindamycin, and metronidazole.

Evaluation of Sch 29,482 in the eradication of Neisseria meningitidis from nasopharyngeal carriers

Fifty-eight chronic carriers of Neisseria meningitidis were given 250 mg of Sch 29,482 or placebo orally every 6 h for 4 days. Although 22 of 29 subjects taking Sch 29,482 became culture negative while taking the drug, only five were culture negative 2 weeks posttherapy. There were no significant adverse reactions.

Comparative in vitro activity of Sch 29,482, a new oral penem, against Neisseria gonorrhoeae

The in vitro activity of Sch 29,482, a new oral beta-lactam antimicrobial agent, was compared with those of norfloxacin, rosoxacin, ampicillin, erythromycin, and tetracycline against 142 Neisseria gonorrhoeae strains. Sch 29,482 was as active as norfloxacin and rosoxacin. Its activity was greater than the other three antimicrobial agents. It inhibited 90% of the isolates, regardless of beta-lactamase activity, at a concentration of less than or equal to 0.06 micrograms/ml.