Qualaquin, the only formulation of quinine sulfate available in the US, is approved only for treatment of uncomplicated malaria, but most prescriptions for its use are written for treatment or prevention of nocturnal leg cramps. The FDA recently issued a warning about its safety.

Between April 2005 and October 2008, 38 cases of serious or life-threatening adverse effects of quinine were reported to the FDA. Twenty-one of these patients had thrombocytopenia and required hospitalization. Two deaths were reported: one from hemolysis and the other from thrombotic thrombocytopenic purpura (TTP). Some patients developed mucosal bleeding (gingival, gastrointestinal, epistaxis), hemoptysis, petechiae or ecchymosis. The median time to onset of adverse effects after starting quinine was about 13 days. Most patients with thrombocytopenia recovered when quinine was stopped.1 In addition to hematologic toxicity, quinine can cause cinchonism (tinnitus, headache, disturbed vision and nausea) and QT prolongation.

1. FDA drug safety communication: new risk management plan and patient medication guide for Qualaquin (quinine sulfate). Available at www.fda.gov/Drugs/DrugSafety/PostmarketDrugSafetyInformationforPatientsandProviders/ucm218202.htm. Accessed October 25, 2010.