Effect of a lactobacillus preparation on the absorption of oral ampicillin

Lactobacillus preparations have been demonstrated to be beneficial in the prevention of antibiotic-associated diarrhea resulting from ampicillin. Since the bioavailability of oral ampicillin is known to be affected by food and fluid volume, a study to evaluate the influence of a lactobacillus product on ampicillin bioavailability was performed. Twelve healthy volunteers, male and female, were studied in a randomized three-way cross-over study. Each received ampicillin alone, ampicillin with a lactobacillus preparation, and ampicillin followed 1 h later by the lactobacillus preparation. Blood was sampled over a 6-h time period. Ampicillin content was determined by high-pressure liquid chromatography. Area under the concentration-time curve, area under the first moment of the concentration-time curve, maximum concentration of drug in plasma, time to maximum concentration of drug in plasma, and mean residence time were determined for each study interval. No differences in maximum concentration of drug in plasma, time to maximum concentration of drug in plasma, area under the concentration-time curve, or mean residence time were seen for either males or females or the combined group. The lactobacillus preparation as used in this study did not appear to interfere with the bioavailability of oral ampicillin.