Comparative pharmacokinetics of dicloxacillin and ampicillin between individual and combined doses

Pharmacokinetics of dicloxacillin and ampicillin dosed individually and in combination were investigated by means of moment analyses of urinary excretions of intact forms and metabolic products of parent penicillins. Comparison of excretion profiles between individual and combined doses to human subjects indicated that the transformation of ampicillin to penicilloic acid and subsequent conversion to secondary metabolite are suppressed by the simultaneous dose of dicloxacillin, while the total excretion ratio to dose and the mean residence times in the body remain almost unchanged. The excretion profiles of dicloxacillin and metabolites are not significantly affected by the combined dose.