Abstract:
The pharmacokinetics of ampicillin and bacampicillin were studied in 14 healthy Thai volunteers using a randomized crossover design. Serum levels of ampicillin and the amount excreted in urine were determined simultaneously. A one-compartment open model was used to characterize the pharmacokinetic data. Following an oral administration of bacampicillin 400 mg, ampicillin 250 and 500 mg, the mean individual peak serum concentrations were 5.98 ± 0.38 mcg/ml, 2.04 ± 0.23 mcg/ml and 3.93 ± 0.49 mcg/ml respectively while the time required to reach the peak were 0.82 ± 0.07 hr, 1.68 ± 0.16 hr and 1.71 ± 0.07 hr respectively. More complete oral absorption of bacampicillin than ampicillin was also evident by higher AUC0∞ and higher percentage urinary recovery obtained after oral administration of bacampicillin. Pharmacokinetic parameters concerning distribution and elimination of ampicillin obtained after the administration of either one of the two drugs were not significantly different. He study of dose-drug concentration relationship by giving two progressive doses of ampicillin 250 and 500 mg and bacampicillin 400 and 800 mg showed a linear increase in the peak serum levels and the AUC0∞ with the increased dose. Food neither delayed nor decreased the oral absorption of bacampicillin as evidenced by the insignificant differences in the peak serum levels (6.33±0.48 mcg/ml, 7.07±1.34 mcg/ml for fasting and non-fasting), the peak time (0.89±0.05 hr, 0.96±0.10 hr for fasting and non-fasting), The AUC0∞ (10.59±0.89 hr.mcg/ml, 11.46±1.31 hr.mcg/ml for fasting and non-fasting), and the percentage urinary recovery of ampicillin (58.22±6.68, 57.32±8.09 for fasting and non-fasting). The pharmacokinetic parameters obtained from urinary excretion data corresponded very well with those obtained from serum data, it is therefore suggested that one can describe the pharmacokinetic appearance of ampicillin and bacampicillin by means of complete urine collection instead of obtaining the serum samples.
