Characterization of intestinal absorption and enterohepatic circulation of mycophenolic Acid and its 7-O-glucuronide in rats.

To assess the mechanism of gastrointestinal disorders by mycophenolate mofetil (MMF), the intestinal absorption and enterohepatic circulation of mycophenolic acid (MPA), an active metabolite of MMF, and its 7-O-glucuronide (MPAG) were investigated using rat intestinal loops and a linked-rat model. The stability of MPAG in the intestinal fluids, the toxicity of MPA and MPAG to intestinal mucosa, and biliary excretion of MPAG in rats with acute renal failure (ARF) were also characterized. MPA was rapidly and extensively absorbed from the rat intestine whereas MPAG was much less absorbable. When MPA was administered intravenously to bile-donor rats, 1.2% of dose was excreted in bile of receiver rats exclusively as MPAG during 4 h. MPAG was minimally deconjugated in the intestinal fluids. MPAG, but not MPA, significantly enhanced the release of lactate dehydrogenase from intestinal mucosa. When MPA was intravenously administered to ARF rats, the biliary excretion of MPAG significantly increased, compared with that in normal rats. These results demonstrated that MPAG accumulated in the intestinal lumen following biliary excretion and exerted some toxic effect on the intestinal mucosa. It was also suggested that enterohepatic circulation of MPAG under renal dysfunction increased the risk of gastrointestinal disorders due to MPAG.