Aims: To evaluate drug-drug interactions between carotegrast methyl, a CYP3A4 inhibitor, and other CYP3A4 substrates, midazolam, atorvastatin, and prednisolone. Methods: A total of 88 healthy volunteers orally received carotegrast methyl 960 mg three times daily for 14 days. A single oral (5 mg) or intravenous (0.017 mg kg^-1) midazolam, oral (5 mg) prednisolone, or oral (10 mg) atorvastatin was administered before, with, and after carotegrast methyl treatment. When the 90% confidence interval (CI) for the geometric mean ratios of the pharmacokinetic (PK) parameters with coadministration with carotegrast methyl (day 14) to those before carotegrast methyl administration was between 0.80 and 1.25, no PK interaction were deemed. Results: The C_max and AUC_0-t of oral midazolam before administration of carotegrast methyl was 30.9 ± 9.8 ng mL^-1 and 74.5 ± 21.9 ng h mL^-1, respectively. The geometric mean ratio of the C_max and AUC_0-t of midazolam on day 14 to those on day -1 was 1.86 (90% CI, 1.64 – 2.11) and 3.07 (90% CI, 2.81 – 3.35), which did not fall within the range of 0.80 – 1.25, suggesting that carotegrast methyl had a PK interaction with midazolam. Similar PK interactions were found for intravenous midazolam and atorvastatin, but not for prednisolone. The inhibitory effect of carotegrast methyl on CYP3A4-mediated metabolism of midazolam and atorvastatin had almost disappeared by 14 days after the end of administration. Conclusion: Carotegrast methyl was classified as a moderate CYP3A4 inhibitor in humans. Carotegrast methyl might enhance the action of drugs that are metabolized by CYP3A4.