Use of Malaria Drug Qualaquin for Leg Cramps May Cause Blood Disorders

Federal regulators are warning doctors not to use the malaria drug Qualaquin to treat leg cramps, due to the risk of potentially life-threatening blood disorders and kidney damage. 

The FDA released a drug safety communication for Qualaquin (quinine sulfate) on Thursday. In the communication, the FDA notes that doctors have been prescribing Qualaquin “off label” for the treatment of leg cramps, but they warn that the drug should not be prescribed for this purpose because it carries a risk of life-threatening blood and kidney problems that can lead to permanent injury or death. At least two people have died from Qualaquin side effects since 2005.

Qualaquin, distributed by AR Scientific, was approved by FDA in 2005 for the treatment of uncomplicated malaria caused by the parasite Plasmodium falciparum. There are only about 1,500 such cases in the U.S. per year, mostly the result of people traveling to malaria-infested areas, according to the U.S. Centers for Disease Control and Prevention (CDC). However, once a medication is approved, U.S. doctors are allowed to prescribe drugs “off-label” for whatever purposes they deem necessary

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The FDA said it received 38 adverse event reports of serious side effects of Qualaquin from April 2005 through October 1, 2008. Most of the cases were serious and life-threatening reactions due to low levels of platelets in the blood, a condition known as thrombocytopenia, and Hemolytic-uremic syndrome (HUS), which causes clots in small blood vessels and kidney damage. Some of the cases led to permanent kidney damage, hospitalization and, in two cases, death.

According to the FDA, most of the cases were situations where people were prescribed the drug “off-label” for the treatment of leg cramps.

The FDA required AR Scientific to create a risk evaluation and mitigation strategy (REMS) designed to reduce the risk to patients. The REMS requires that patients be given a medication guide that explains the approved uses of Qualaquin and its potential side effects. The company will also have to send a letter to health care providers that warns them of the potential side effects.


  • SteveApril 26, 2020 at 12:02 pm

    I have taken Qualaquin or Quinine Sulf for years for leg cramps, up only when I feel cramps coming on and never on a daily basis. My blood work has been excellent for as long as I can remember.

  • DorrFebruary 24, 2011 at 9:08 pm

    My wife died in October 2009 she was taking qualaquin daily for years for leg cramps. She developed a clotting disorder and amongst her other health conditions she clotting disorder kept her from remaining on temporary life support and she die. She had 2 children ages 10 and 13.

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