Maternal blood concentration of tadalafil in pregnancy: Comparison of pregnant and non-pregnant women

In this study, the drug kinetics of tadalafil were compared between pregnant and non-pregnant women to determine the ideal dosage to promote uterine blood flow.We recruited five pregnant and five non-pregnant women, all of which were administered tadalafil (20 mg/day). The blood concentration of tadalafil was measured 1, 2, 4, 6, 8, and 24 h after administration. We investigated the side effects within 4 days of tadalafil administration and compared the cumulative frequency between the two groups.The mean area under the concentration-time curve and maximum blood concentration of tadalafil were not different between the pregnant and non-pregnant groups. Time to maximum blood concentration was delayed by 1 min on average in the pregnant group compared with the non-pregnant group. The cumulative frequency of side effects was significantly lower in the pregnant group than in the non-pregnant group (P = 0.026). No side effects were observed in either group after the fifth day of the tadalafil administration.Although there was no difference in maximum blood concentration between non-pregnant and pregnant women, the rate of side effects was lower in pregnant women than in non-pregnant women. Therefore, pregnant women may tolerate tadalafil better.