7-Monohydroxyethylrutoside Protects against Chronic Doxorubicin-induced Cardiotoxicity When Administered Only Once Per Week

Doxorubicin is a very effective antitumor agent, but its clinical use is limited by the occurrence of a cumulative dose-related cardiotoxicity, resulting in congestive heart failure. 7-Monohydroxyethylrutoside (monoHER), a flavonoid belonging to the semisynthetic hydroxyethylrutoside family, has been shown to protect against doxorubicin-induced cardiotoxicity when administered i.p. at a dose of 500 mg/kg five times/week in combination with a weekly i.v. dose of doxorubicin. Such a dosing schedule would be very inconvenient in clinical practice. We therefore investigated a dosing schedule of one administration of monoHER just before doxorubicin. The electrocardiogram was measured telemetrically in mice after the combined treatment of doxorubicin (4 mg/kg, i.v.) with one dose of monoHER (500 mg/kg, i.p., administered 1 h before doxorubicin) for 6 weeks. These data were compared with the five times/week schedule (500 mg/kg, i.p., administered 1 h before doxorubicin and every 24 h for 4 days). The increase of the ST interval was used as a measure for cardiotoxicity. It was shown that 500 mg/kg monoHER administered only 1 h before doxorubicin provided complete protection against the cardiotoxicity. This protection was present for at least 10 weeks after the last treatment. Because of the short half-life of monoHER, these results suggest that the presence of monoHER is only necessary during the highest plasma levels of doxorubicin.