Off-Label Use of Malaria Drug Puts Patients at Risk For Blood Disorders, FDA SaysJul 9, 2010 | Parker Waichman LLP
U.S. health regulators warned today that people who use the malaria drug Qualaquin to treat night time leg cramps face a serious risk of life-threatening blood disorders. AR Scientific, which distributes Qualaquin in the U.S., has developed a risk management plan aimed at educating health care professionals and patients about the potential risks.
According to a posting on the FDA Website, Qualaquin is ONLY approved for the treatment of uncomplicated malaria caused by the parasite Plasmodium falciparum. Only about 1,500 people in the U.S. are diagnosed with this condition each year, and most of those are travelers returning from malaria-endemic areas.
In the U.S., the majority of Qualaquin prescriptions are written for the treatment or prevention of night time leg cramps or Restless Leg Syndrome. Qualaquin has not been approved to treat night time leg cramps, the FDA said. However, physicians are legally permitted to prescribe approved drugs in anyway they see fit.
According to the FDA, a review of reports submitted to the agency’s adverse-event reporting system from April 2005 to October 1, 2008 found 38 cases of serious adverse events associated with quinine, the active drug in Qualaquin. The majority of patients (25) took quinine to prevent or treat leg cramps or Restless Leg Syndrome; only 1 patient was taking quinine for the treatment of malaria.
Reported reactions included including serious bleeding due to a severe lowering of blood cells called platelets (thrombocytopenia), and a condition known as hemolytic-uremic syndrome/ thrombotic thrombocytopenic purpura, which in some cases may result in permanent kidney damage. Twenty-one patients were diagnosed with thrombocytopenia, and 18 of those patients required hospitalization. Most of the patients with thrombocytopenia recovered when quinine was discontinued and other therapeutic interventions were initiated. Two deaths were reported among the blood disorder patients, one of which involved thrombotic thrombocytopenic purpura, and another due to hemolysis.
Quinine adverse event reports also included four cardiovascular events, and 10 miscellaneous adverse events such as gastrointestinal symptoms, hearing loss, rash, electrolyte imbalance, and drug interaction, the FDA said.
According to the FDA, patients being prescribed Qualaquin will now be given a medication guide that explains what the product should and shouldn’t be used for, as well as the potential risks of the product. The agency also said AR Scientific would issue a letter to health-care professionals discussing the risks of using Qualaquin off-label.