Mycophenolic acid is a commonly encountered medication in nephrology. In addition to its use in the vast majority of kidney transplant recipients as part of the immunosuppressive regimen, it is also gaining popularity in the treatment of immune-mediated diseases such as lupus nephritis and ANCA-associated vasculitis.
The drug is usually compared to azathioprine since they both function as antimetabolites, inhibiting purine synthesis in rapidly-dividing cells. However, mycophenolate is more lymphocyte-specific, inhibiting inosine monophosphate dehydrogenase, which controls the rate of synthesis of guanine monophosphate in the de novo pathway of purine synthesis in lymphocytes, and therefore is associated with fewer side effects than azathioprine. It is available as mycophenolate mofetil (Cell Cept, used most commonly) or mycophenolate sodium (Myfortic).
Side effects of MMF: the two main ones are (a) an increased susceptibility to infection--much like all immunosuppressant drugs, and (b) frequent GI side effects such as nausea, vomiting, and diarrhea. There are several options for patients who have intolerable GI side effects: the dose could be lowered or stopped altogether in favor of a different drug such as azathioprine; sometimes spacing out MMF to three or four times a day (instead of the traditional bid dosing) may help, and finally the sodium salt (Myfortic) is allegedly associated with less GI side effects. Finally, MMF is listed as a "Group D" drug (known to be unsafe in pregnancy), so fertile women who get it should be placed on some type of birth control.