Amoxicillin: Laboratory evaluation and pharmacologic study in Thailand

Abstract

The in vitro activity of amoxicillin against 735 clinical isolates in Thailand was evaluated. Blood and urine drug levels were assayed after a single 500 mg oral dose and the serum level was found to be 10 mcg/ml at 2 hours. Urinary concentration was 80 times that of serum at half an hour and 200 times at 2 hours. These findings in normal Thai subjects do not differ greatly from those reported in Western countries. At the blood levels normally achievable, amoxicillin was found to be active against all Gram-positive organisms except Staphylococcus aureus. It was not effective for Enterobacter, Klebsiella, Proteus or Pseudomonas aeruginosa but was found to be active against Salmonella particularly Salmonella typhi. Ten strains of chloramphenicol-resistant S. typhi carried transferable resistance factor (R. factor) to chloramphenicol, but not to amoxicillin. Gram-negative and Gram-positive organism isolated from Thai patients were found to require higher drug concentrations for their inhibition than has been reported for these organisms in the West.