Comparison of amoxicillin and ampicillin in single-dose oral treatment of males with gonococcal urethritis.

Amoxicillin in single oral doses of 2.0 g, 2.0 g plus 1.0 g probenecid, or 3.0 g was compared with ampicillin 3.5 g plus 1.0 g probenecid in the treatment of 203 males with uncomplicated acute gonococcal urethritis. Cure rates above 95% were produced by all treatments except the 2.0-g amoxicillin dose, which cured 89% of patients. Of 198 pretreatment gonococcus isolates tested by an agar dilution technique for susceptibility to penicillin G, ampicillin and amoxicillin, over 50% showed relative resistance (MIC > 0.06 mug/ml) to the antibiotics. However, amoxicillin was somewhat more active against isolates showing considerable resistance (MIC >/= 1.0 mug/ml) to penicillin G or ampicillin. Adverse effects of amoxicillin were few: two patients reported transient nausea and six noted short-lived diarrhea. No hypersensitivity reactions were observed.