Effect of food on bioavailability of nalidixic acid from uncoated tablets having different dissolution rates

The effect of food on the bioavailability of two single lots of commercial tablets and one trial tablet of nalidixic acid, varying widely in drug dissolution characteristics, was determined in healthy male subjects after oral administration. Four subjects received, in a crossover fashion, a single 250 mg dose in an uncoated tablet during periods of fasting and non-fasting. Significant differences in Cmax, Tmax and AUC0-8 were observed between the tablet having the fastest dissolution rate and the other tablets tested, when administered postprandially. Both Cmax and AUC0-8 were significantly increased after administration of the two tablets exhibiting the poorer dissolution characteristics to the non-fasting subjects. However, food was not observed to affect any of the bioavailability parameters after postprandial administration of the tablet exhibiting the fastest dissolution rate. The improvement of bioavailability of the two tablets exhibiting the poorer dissolution by food intake was ascribable to enhanced dissolution of nalidixic acid resulting from vigorous mixing and agitation in the digestive tract. It was concluded that the effect of food on the bioavailability of nalidixic acid from uncoated tablets varies with formulation factors, especially with dissolution characteristics.