BIOPHARMACEUTIC STUDY OF COMMERCIAL NITROFURANTOIN ORAL DOSAGE FORMS

In this work a biopharmaceutic study is performed an two nitrofurantoi n oral dosage forms which are commercialized in Spain : coated tablets (formulation A) and conventional tablets (formulation B). The in vitr o dissolution tests are performed at different pH. The dissolution pro files corresponding to formulation Bare satisfactorily fitted to a fir st order kinetics. The mean dissolution time parameter was independent of pH within the range of pH studied. The dissolution tests performed with coated tablets showed that both the amount of drug dissolved at the end of the the test (8 h) as well as the dissolution efficiency ar e pH dependent within the range studied. The in vivo study of both for mulations was carried our on nine healthy volunteers according to a cr ossover design. Nitrofurantoin levels in urine were anaylsed. The infl uence of two different types of diet, one rich in lipids and the other rich in proteins, was also studied. For both formulations, the type o f diet does not modify the amount of drug absorbed. However, coated ta blets release the drug much more slowly than conventional tablets. The mean ratios (A/B) of X(M)(infinity) (amount of nitrofurantoin excrete d into the urine) and mean residence time, and their 90% confidence li mits, confirm the bioinequivalence between the formulations for the tw o types of diet studied.