Signals from pharmacovigilance studies indicate that women are at higher risk for adverse drug reactions (ADRs) due to diuretics. Despite the long-term use of torasemide, there are few studies investigating gender differences of torasemide pharmacokinetics in the hospital setting. Therefore, torasemide pharmacokinetics were investigated in 90 patients (45 women, 45 men) during steady-state conditions. Torasemide elimination was significantly reduced in women compared with men (eg, body-weight-normalized area under the concentration-time curve: 42.1 +/- 20.4 vs 30.9 +/- 10.3 kg.h/L; P <.001). Among the investigated genetic factors [SLC22A11(OAT4), SLCO1B1(OATP1B1), CYP2C9], only the SLCO1B1c.521T>C polymorphism had a significant influence on torasemide pharmacokinetics. Using cell lines expressing OATP1B1, the authors identified torasemide as OATP1B1 substrate (K(m) = 6.2 microM) with a significant reduction of uptake by the 521C-variant. Taken together, gender differences in torasemide pharmacokinetics are likely to contribute to a higher rate of ADRs in women, which has, for example, been observed in a German Pharmacovigilance Project with 66% of hospitalizations due to torasemide ADRs occurring in women.
