Objective: The aim of this study was to elucidate the effect of the peroxisome proliferator-activated receptor-gamma (PPAR-gamma) activating angiotensin receptor blocker (ARB) telmisartan and the non-PPAR-gamma activating ARB valsartan and candesartan on mycophenolic acid (MPA) pharmacokinetics in renal transplant recipients.
Methods: Recipients (n = 10 each group) were randomly given either 40 mg of telmisartan, 80 mg of valsartan or 8 mg of candesartan cilexetil for at least 6 months, and no ARB. Blood was sampled a year after transplantation.
Results: Dose-adjusted maximum and trough plasma concentration of MPA co-administered with telmisartan were the lowest in all groups. The mean dose-adjusted area under the concentration curve from 0 to 12 h (AUC(0-12)) and AUC(0-6) of MPA co-administered with telmisartan were significantly lower than that without ARB (98 vs. 138 ng x h/mL/mg, P = 0.0353 and 63 vs. 96 ng x h/mL/mg, P = 0.0305). Coadministration of valsartan and candesartan did not alter MPA pharmacokinetics. The AUC ratio of MPA glucuronide (MPAG)/MPA co-administered with telmisartan was higher than that without ARBs, but not significantly (14.2 vs. 9.1). The mean maximum and minimum plasma concentrations of telmisartan (40 mg) after oral administration were 84 and 15 ng/mL, respectively, and that of valsartan (80 mg) 2220 and 441 ng/mL, respectively. Plasma concentrations of candesartan in most transplant patients were not observed 19 h after oral administration of candesartan cilexeil (8 mg).
Conclusions: The degree of drug interaction between MPA and telmisartan was significantly greater than that between MPA and valsartan or candesartan. Uridine diphosphate-glucuronosyltransferase (UGT) 1A9 has been identified as a PPAR-gamma target gene. UGT induction by telmisartan might stimulate MPA glucuronidation. A combination of telmisartan and mycophenolate mofetil might require periodic monitoring of MPA.