Consumer Reports Insights

FDA warnings about quinine don't stop doctors from prescribing it for leg cramps

Tuesday, March 2, 2010

If you suffer from nighttime leg cramps, your doctor might prescribe quinine. The Food and Drug Administration has approved it for only one purpose -- to treat malaria -- but doctors can legally prescribe most medications, including quinine, "off-label" for any treatment they deem appropriate.

Leg cramps are uncontrolled muscle contractions so painful that they can awaken you from sleep. They occur in many adults and are reported more often by women, and especially pregnant women. Since the 1940s, doctors have been prescribing quinine for leg cramps because there are no other reliable treatments.

The FDA has issued warnings about the risks of quinine since 1994 and more recently about its minimal effectiveness in treating leg cramps. In 2006, it banned the sale of all drugs containing quinine except the branded drug Qualaquin because of the risk of serious side effects or death. Yet in the first six months of 2008, more than 124,000 people in the United States received close to 300,000 prescriptions for Qualaquin, according to the FDA. Since the Centers for Disease Control and Prevention reports that only about 1,500 individuals in the United States received malaria diagnoses in 2008, it appears that quinine is still frequently prescribed off-label.

Indeed, from January 2006 to June 2008, 62 percent of quinine prescriptions were for musculoskeletal symptoms, mainly for nocturnal leg cramps. Of the 38 reports of serious adverse events received by the FDA in roughly the same time period, 55 percent were from people who had taken quinine for leg cramps.

Yet there is little convincing evidence for prescribing quinine for leg cramps. Studies of patients with nocturnal leg cramps have been small; they were not randomized, controlled trials; and they had other shortcomings. Quinine also isn't effective for restless legs syndrome (RLS), a neurological disorder characterized by an uncontrollable impulse to keep moving your legs even when you are sitting or trying to go to sleep. The FDA recently sent out an alert that the risk of severe side effects from quinine outweighed any potential benefit for these conditions. (With malaria, the benefit of the drug is considered likely to outweigh its risks.)

Some of quinine's more serious side effects, which can result in hospitalization, serious illness and death, include thrombocytopenia (decreased blood platelets), cardiac problems (including abnormal heart rhythms), kidney failure, rashes and other allergic reactions. Quinine can also interact with other medications, including anti-arrhythmics, digoxin and blood thinners.

Before starting any treatment for nighttime leg cramps (Vitamin B complex and a blood pressure medication called diltiazem are sometimes recommended, although evidence of their effectiveness is minimal), your doctor should rule out any underlying diseases or drug side effects that might be causing them. Conditions that can trigger leg cramps include movement disorders (dystonia); problems with the amount of minerals and fluids in the body (electrolyte imbalance); diabetes; nerve damage or pain; inflammation in various parts of the body; liver or thyroid disease; and disease of the blood vessels.

Cramps can also be caused by certain medications or entire groups of drugs. Among these are individual drugs such as lithium and nicotinic acid (niacin); statins, used to treat high cholesterol; corticosteroids such as prednisone, used to reduce inflammation for conditions including arthritis, asthma, lupus and rashes; diuretics, such as hydrochlorothiazide and furosemide (Lasix and generics), used to treat high blood pressure and heart failure; and phenothiazines, which are tranquilizing drugs. Drinking alcohol can also trigger leg cramps.

Bottom line: Quinine is widely prescribed to treat leg cramps (and, less frequently, other cramping disorders) even though the FDA and the drug's prescribing information specifically caution that it should not be prescribed for those conditions. Consumer Reports' medical advisers suggest talking with your doctor about all drug and non-drug treatments for leg cramps. The risk of serious or life-threatening side effects from quinine and the lack of convincing evidence for its use outweigh the potential benefit of the drug for any condition except malaria.

Copyright 2010. Consumers Union of United States Inc.

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