Mycophenolate mofetil is available now as a generic alternative to Cellcept. I'm finding that many physicians are opposed to the switch. Why is this if bioequivalence has been established by the FDA?
In order for a generic drug to be approved by the FDA, it needs to demonstrate bioequivalence with the reference drug. In other words, the rate and extent of absorption of the generic drug can not be significantly different from the reference drug when given at the same molar dose under the same conditions. Bioequivalence for the generic drug is established in a single study of 24-36 healthy volunteers. It is determined by determining the mean AUC and Cmax for the generic drug and comparing it the reference drug. The ratio of bioavailability of the generic drug to the reference drug (T/R ratio) must fall between the confidence interval of 80-125% for the generic drug to get FDA approval.
The FDA does not usually require manufacturers of generic drugs to perform safety or efficacy studies in humans or in this particular case, transplant patients. For this reason, some transplant physicians are reluctant to use generic mycophenolate mofetil since no efficacy studies were perform in transplant patients prior to the release of these drugs into the market.