Cochrane corner commentary: Quinine for muscle cramps

Muscle cramps are sudden and involuntary contractions of one or more muscles, usually in the leg and particularly the calf. They can be a symptom of an underlying condition, such as arteriosclerosis or a side effect of a medication, such as diuretics, but this is unusual and most cases are idiopathic. Studies have found that idiopathic leg cramps are very common, occurring in 33–95% of adults [1]. They are slightly more common in women, are more likely with increasing age, occur in many pregnant women during the last trimester, and around 75% of cramp episodes occur at night [1]. The mean duration per episode is just under 10 min. Quinine, derived from cinchona bark, has traditionally been used as a treatment for this condition, but studies have found conflicting data, both in terms of efficacy and safety. This Cochrane review, which assessed the evidence concerning the effect of quinine on muscle cramps, is therefore very useful for clinicians, particularly family doctors [2]. For studies to be included in the review they had to be ‘‘randomised controlled trials of people of all ages with muscle cramps in any location and of any cause, treated with quinine or its derivatives.’’ This resulted in 23 trials with a total of 1586 participants being included in the review. Most of the studies compared quinine to placebo and the most commonly used dose of quinine used was 300 mg/day, with a range of 200–500 mg. The authors noted that the risk of bias in the trials varied considerably, as although all 23 trials claimed to be randomised, only a minority described randomisation and allocation concealment in adequate details. In terms of efficacy, the main finding was that, compared to placebo, quinine significantly reduced the number of cramps by 28%, the intensity of cramps by 10%, and the number of days when a cramp occurred by 20%. However, the duration of cramp episodes was not significantly affected. With respect to side effects, more people taking quinine experienced minor adverse events