Malaria drug quinine (Qualaquin) for nocturnal leg cramps? Check again!

July 8, 2010 ­ Physicians should not prescribe the malaria drug quinine (Qualaquin) for nocturnal leg cramps ­ an off-label use ­ because it may result in serious and life-threatening hematologic adverse effects, the US Food and Drug Administration (FDA) announced today.

Quinine, marketed by AR Scientific, is approved only for uncomplicated malaria caused by the parasite Plasmodium falciparum, according to the agency.

The FDA issued a similar warning in 2006, but the agency noted today that the majority of quinine used in the United States is still for the prevention or treatment of leg cramps.

Quinine therapy may result in thrombocytopenia, which can cause serious bleeding, or hemolytic-uremic syndrome/thrombotic thrombocytopenic purpura, which may lead to permanent kidney damage. The FDA said that it received 38 reports of serious adverse events associated with quinine between April 2005 and October 1, 2008, in the United States through its Adverse Event Reporting System. Only 1 patient was taking quinine to treat malaria. Two patients died.

Under a risk management plan approved by the agency, the drug’s manufacturer will issue a letter to prescribers warning of the risk for hematologic reactions to the drug. In addition, patients must be given a medication guide explaining what quinine is and is not approved for, and its potential adverse effects.

To report any adverse events related to quinine, contact MedWatch, the FDA’s safety information and adverse event reporting program, by telephone at 1-800-FDA-1088, by fax at 1-800-FDA-0178, online at http://www.fda.gov/medwatch, or by mail to MedWatch, FDA, 5600 Fishers Lane, Rockville, Maryland 20852-9787.