Enalapril in RAPIDISC (wafer formulation): pharmacokinetic evaluation of a novel, convenient formulation

Background: Enalapril in RAPIDISC* (wafer), a new easy-to-administer formulation of enalapril, may improve the convenience of enalapril therapy, thereby helping patients adhere to antihypertensive treatment. Subjects and methods: To determine whether 20 mg enalapril wafer is bioequivalent to the conventional 20 mg enalapril tablet, an open-label, two-period crossover study was performed in 16 healthy male volunteers. Cumulative urinary recovery of free enalaprilat (active metabolite of enalapril) and the serum maximum concentration of free enalaprilat (C-max,,) were the primary pharmacokinetic parameters used to determine bioequivalence in this study. Bioequivalence was defined as the geometric mean ratio (wafer : tablet) falling within the equivalence limits of 0.80 to 1.25 for both parameters. Results: Cumulative urinary recovery of free enalaprilat (0 - 72 hours) was similar between the wafer and conventional tablet formulations (arithmetic mean 5.13 vs. 5.03 mg, about 36% of dose). The geometric mean ratio of the urinary recovery of free enalaprilat (wafer: tablet) was 1.03 (90% CI: 0.93, 1.15). C-max of serum enalaprilat was also similar between the wafer and conventional tablet formulations (arithmetic mean 85.7 vs. 76.3 ng/ml). The geometric mean C-max ratio (wafer : tablet) was 1.10(90% CI: 1.00, 1.22). Both enalapril formulations were well tolerated. Conclusion: This study demonstrates that 20 mg enalapril in RAPIDISC is bioequivalent to 20 mg enalapril conventional tablet.