To provide a medicament for safely treating a patient in need of treatment with pemafibrate, a salt thereof, or a solvate of any of these (hereinafter also referred to as pemafibrate therapy).A medicament for treating a patient in need of pemafibrate therapy, the medicament comprising the step of avoiding or suspending concomitant use of pemafibrate, a salt thereof, or a solvate of any of these as an active ingredient in order to suppress an increase in plasma concentration of pemafibrate when the treatment is combined with a medicament containing an OATP1B inhibitor, or the step of reducing the dose of pemafibrate, a salt thereof, or a solvate of any of these.
