Background: Metoclopramide is mainly metabolized by CYP2D6, CYP3A4, CYP2C19, and CYP1A2
enzymes, while cilostazol is also metabolized by CYP3A4, CYP2C19, and CYP1A2 enzymes.
Aim: This study evaluates the effect of cilostazol on the pharmacokinetics of oral metoclopramide.
Methods: This was a randomized, two-phase cross-over pharmacokinetic study separated by a 4-week wash-out time
period, 12 healthy non-smoking volunteers received metoclopramide 20 mg as a single oral dose and after 4 weeks,
cilostazol 100 mg twice daily for 4 days then with metoclopramide 20 mg on test day. Serial blood samples were
analyzed by using a validated high-performance liquid chromatography-ultraviolet method to determine maximum
plasma drug concentration (Cmax), time to reach (Tmax), and area under the curve (AUC0-∞) of metoclopramide.
Results: Cilostazol increased the mean Cmax, AUC0-∞ and half-life (T1/2) of metoclopramide by 6%, 27% and by
0.79 %, respectively. In addition, Tmax of metoclopramide was delayed by cilostazol.
Conclusion: The results showed delayed Tmax of metoclopramide by cilostazol, which could lead to the conclusion
that cilostazol affects the absorption of metoclopramide. Both drugs when necessary to administer together must not
be administered at the same time especially when given in gastroparesis patients.