Effect: Itraconazole may increase the plasma concentration of alosetron.
Clinical management: Caution should be exercised upon coadministration of these drugs. Monitor for increased alosetron toxicity (e.g. bowel side effects: obstipation, abdominal or gastrointestinal pain or discomfort, nausea, abdominal distention, reflux and hemorrhoids) and adjust dose if necessary.
Probable mechanism: Inhibition of the cytochrome P450 (CYP) 3A4-mediated biotransformation by itraconazole.
Summary: Although not studied for itraconazole, coadministration of ketoconazole (200 mg BID for 7 days) and alosetron (1 mg single dose on day 7) increased alosetron AUC by 29% in 38 healthy female subjects. Coadministration with the CYP3A4-inhibitor itraconazole could result in similar effects.
QT effectItraconazole: Conditional QT risk
Substantial evidence reports that this drug causes QT prolongation and has a risk of TdP, but only under certain known conditions (e.g. excessive dose, drug interaction, etc.).