In vitro activity, pharmacokinetics and therapeutic efficacy of azithromycin

Abstract

We evaluated the usefulness of azithromycin (AZM), a new azalide derivative, in respiratory tract infections. The MIC₅₀, MIC₇₀ and MIC₉₀ (μg/ml) of AZM were 0.78, 3.13 and >100 against Methicillin sensitive Staphylococcus aureus (26 strains), >100, >100 and >100 against Methicillin resistant Staphylococcus aureus (22 strains), 0.10, 1.56 and 3.13 against Streptococcus pneumoniae (46 strains), 1.56, 3.13 and 6.25 against H. influenzae (41 strains), 0.05, 0.05 and 0.05 against Moraxella catarrhalis (45 strains), >100, >100 and >100 against Pseudomonas aeruginosa (46 strains), respectively. The activity were comparable with or superior to those of erythromycin and roxithromycin.
The pharmacokinetics of AZM were studied in three patientswith chronic respiratory infections. The maximum sputum level in the patient after 250 mg oral administration once per day were 0.24μg/ml. The maximum sputum level in other patients after oral administration of 500mg were 1.60μg/ml and 3.54 μg/ml. The maximum serum level were 1.84μg/ml at two hours after oral administration of 500mg.
9 cases with lower respiratory tract infections were studied for the clinical evaluation of AZM. AZM were given orally at 250 or 500mg per day for 3 days. The causative organisms were S. pneumoniae (1 case), H. influenzae (3 cases), M. catarrhalis (2 cases), Corynebacterium pseudodiphtheriticum (1 case) and Acinetobacter haemolyticus (1 case). AZM were clinically effective on the 8 cases of the 9. Only 1 strain of H. influenzae were not eradicated. No adverse reactions were observed.
We concluded that AZM is a very useful oral antimicrobial agent for the treatment of respiratory tract infections.