No effect of omeprazole-induced hypoacidity on the bioavailability of amoxycillin or bacampicillin

The absorption of ampicillin esters is reported to decrease when gastric acidity is inhibited because of hydrolysis of the esters, or by lowered solubility at a higher pH. No such information on the hydroxylated derivative amoxycillin is available. This was investigated in 8 fasting volunteers, who received 800 mg bacampicillin or 1000 mg amoxycillin on 4 study days, separated by at least 1 week. Each ampicillin derivative was administered on 1 occasion as a single drug, and on another after 1 week's pretreatment with the potent acid inhibitor omeprazole. Bacampicillin was absorbed more rapidly than amoxycillin, and serum peak concentrations were higher. After induced hypoacidity, peak concentrations of both antibiotics appeared to be slightly delayed, and those of bacampicillin significantly reduced. Nevertheless, both the areas under the plasma concentration curves, and the half lives of elimination of the antibiotics were unaffected. Hypoacidity as such does not reduce the bioavailability of amoxycillin or bacampicillin.