Abstract
We performed laboratory and clinical studies on ritipenem acoxil, a new oral penem, in order to evaluate its usefulness in respiratory tract infections. We determined the antibacterial activity of ritipenem acoxil against respiratory pathogenic bacteria: its MIC50 and MIC90 were 0.05 and 1.56μg/ml against Streptococcus pneumoniae (50 strains), 1.56 and 3.13μg/ml against Haemophilus influenzae (42 strains), 0.2 and 0.78μg/ml against Moraxella catarrhalis (41 strains), 0.2 and 0.78μg/ml against methicillin-susceptible Staphylococcus aureus (28 strains) and 100 and >100μg/ml against methicillin-resistant Staphylococcus aureus (25 strains). However the MICs of 11 strains of methicillin-resistant Staphylococcus aureus were less than 3.13μg/ml.
The maximal serum level of ritipenem acoxil was 1.41 μg/ml, and its maximal sputum level was 0.12μg/ml after a single dose of 400 mg.
Eleven patients with respiratory infections were studied for the clinical evaluation of ritipenem acoxil, which was administered at a dose of 200 mg, 300 mg or 500 mg t.i.d. The clinical efficacy was excellent in 1, good in 6, fair in 1 and poor in 3 patients. The overall efficacy rate was 63.6%.
The causative bacteria were Streptococcus pneumoniae (3), Haemophilus influenzae (3), Moraxella catarrhalis (5), Staphylococcus aureus (1) and Pseudomonas aeruginosa (2). After ritipenem acoxil administration, 7 of 14 strains (50.0%) were eradicated.
There were no side effects or abnormal laboratory findings in patients after the administration of ritipenem acoxil.
We conclude that a daily dose of ritipenem acoxil in the treatment of acute and chronic respiratory infection was 300 mg (t.i.d.) and 500 mg (t.i.d.), respectively.
