Abstract
A basic investigation of ritipenem acoxil, a new penem antibiotic developed for oral administration, was conducted. In addition, we examined its clinical efficacy in treating respiratory tract infections.
1. Antimicrobial activity
The minimum inhibitory concentrations (MICs) of 761 strains of bacteria belonging to 19 genera, which were isolated from clinical specimens, were measured according to the standard procedure described by the Japan Society of Chemotherapy. The antimicrobial activity of ritipenem acoxil was compared with that of cefteram (CFTM) and cefpodoxime (CPDX). Ritipenem acoxil showed excellent antimicrobial activity against gram-positive cocci. Its activity against gram negative rods, excluding Proteus mirabilis and Haemophilus influenzae, was equivalent to or greater than that of the other two antibiotics. As with CFTM and CPDX, ritipenem acoxil was ineffective against Pseudomonas aeruginosa and Xanthomonas maltophilia. Ritipenem acoxil was most effective against Moraxella catarrhalis and Bacteroides fragilis.
2. Concentration of ritipenem acoxil in blood and sputum
Ritipenem acoxil was orally administered to 1 patient with chronic bronchitis and another patient with diffuse panbronchiolitis, at doses of 200mg and 400mg, respectively. The drug concentrations in blood and sputum were serially measured. The peak blood concentration was 1.48μg/ml (4 hours after administration) in the patient with chronic bronchitis who received 200mg of ritipenem acoxil. The peak blood concentration was 0.28μg/ml (2 hours after administration) in the patient with diffuse panbronchiolitis who received 400mg of the antibiotic. The concentration of ritipenem acoxil in sputum in both patients was below the detectable level.
3. Clinical results
The clinical efficacy of ritipenem acoxil was evaluated in 9 patients with respiratory tract infections. The orally administered dose of the antibiotic ranged from 200mg to 400mg, and the agent was given 3 times per day. The duration of administration ranged from 3 to 14 days. Ritipenem acoxil was good in 5 patients, fair in 1 patient, and poor in 2 patients. Clinical efficacy of the antibiotic could not be determined in 1 patient. No adverse clinical or laboratory finding was observed during or after the administration of ritipenem acoxil, except for 1 case of eosinophilia which was judged to be clinically insignificant.
