A literature search from 1993 to 1997 using MEDLINE and keywords beverages, muscle cramps, and quinine was performed. Three beverages containing quinine were examined in grocery stores. Analysis indicated that leg cramps are a common phenomenon associated with many comorbid disorders especially peripheral vascular and neurologic disorders. Thus, evaluation of a patient's complaining of leg cramps appropriately includes vascular, neurologic, and musculoskeletal examinations. Laboratory investigation of the symptom of leg cramps warrants as a minimum, assessment of thyroid function and determination of platelet counts and serum levels of electrolytes, calcium, and magnesium. A few small studies suggest that quinine is effective in decreasing the frequency of nocturnal leg cramps but not their severity or duration. Quinine consumed in commercial beverages has been reported to cause potentially fatal immunologically mediated hypersensitivity reactions. The concentration of quinine in commercial beverages varies greatly. Although commercial beverages containing quinine generally are labeled "Contains quinine," they typically lack both nutritional information about the amount of quinine and warnings of the health risks. It appears that 325 milligrams of quinine taken by mouth at bedtime typically relieves nocturnal leg cramps, but lower starting doses are appropriate for senior citizens and individuals with impaired renal function. In general, quinine in any form should be avoided by pregnant women and people with hepatic failure. Quinine consumed for the treatment of leg cramps should be prescribed and monitored by physicians, and people who consume quinine in commercial beverages must be warned of the health risks.
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