Quinine sulfate (Qualaquin), approved for the treatment of uncomplicated malaria caused by Plasmodium falciparum, is often used off label in the United States to treat nighttime leg cramps. The Food and Drug Administration (FDA) doesn't support this off-label use, a decision based on its review of 38 reports of serious adverse events received between April 2005 and October 2008; 25 of the patients were taking quinine sulfate for nighttime leg cramps. Twenty-one patients developed thrombocytopenia; in two cases the patients developed thrombotic thrombocytopenic purpura, and in two cases the patients developed idiopathic thrombocytopenic purpura. Twelve of the cases involved bleeding (of the gums, nose, or gastrointestinal tract), hemoptysis, petechiae, or ecchymosis. Most of the patients with thrombocytopenia recovered when quinine was discontinued.

A medication guide explaining this risk and encouraging patients to discuss other treatment options for leg cramps with their provider has been created by the FDA and will be distributed with each prescription for quinine sulfate. Nurses should teach patients taking quinine sulfate-for either malaria or nighttime leg cramps-to report easy bruising; severe nosebleeds; blood in the urine or stool; bleeding of the gums; or unusual brown, purple, or red spots on their skin to their provider at once.

To read the FDA Drug Safety Communication, go to http://bit.ly/9LXdH5.