Effect of formulation and process variables on bioequivalency of nitrofurantoin I: preliminary studies.

Fifty-two combinations of nitrofurantoin were developed to assess the effect of dosage form type, particle size, diluent, and process on in vitro availability. With the official procedure and conditions, dissolution rates fell in a 66-fold range. Statistical analysis of the dissolution rates indicated no significant differences as a result of particle size, processing method, or compression force. The diluent choice and dosage form type significantly influenced the dissolution rate. Based on in vitro screening, six formulations presenting a broad range of dissolution rates were selected for further study relating to human bioavailability and bioequivalence.