Proton Pump Inhibitor Co-medication Reduces Active Drug Exposure in Heart Transplant Recipients Receiving Mycophenolate Mofetil

Background. Proton pump inhibitors (PPIs) are often prescribed for gastrointestinal discomfort after heart transplantation. This study investigated the impact of PPI use on mycophenolic acid (MPA) pharmacokinetics in heart transplant recipients receiving mycophenolate mofetil (MMF) in combination with a calcineurin inhibitor (tacrolimus [TAC]/cyclosporine [CsA]) or mammalian target of rapamycin inhibitor (sirolimus/everolimus). Methods. Abbreviated MPA areas under the curve (AUCs; 0, 30, and 120 minutes after morning intake) were obtained in 19 patients on a PPI (initial examination) and 1 month after PPI discontinuation (follow-up). Mean patient age was 58.2 +/- 8.8 years, and mean time after transplantation was 2.3 +/- 4.0 years (range, 0.2-13.0 years). Results. At initial examination mean daily MMF dose was 2.2 +/- 0.8 g. MMF dose was kept unchanged for the duration of study (P = ns). Mean predose (CO) MPA serum concentrations were insignificantly lower with PPI comedication (2.5 +/- 2.2 mg/L vs 2.8 +/- 1.7 mg/L; P = .15). Dose-adjusted abbreviated MPA AUCs (adjusted to morning dose) were significantly lower during PPI therapy (45.2 +/- 20.3 vs 65.2 +/- 38.8 mg . h/L . g [MMF]; P = .02). Conclusions. Patients with PPI comedication during MMF therapy show significantly lower exposure to mycophenolic acid determined by dose-adjusted abbreviated MPA AUCs. Although the clinical relevance of this pharmacokinetic interaction was not determined in this study, MPA drug monitoring by limited sampling strategies might be helpful during changes in antacid comedication in patients on MMF.