Quinine for muscle cramps

Cochrane: Muscle cramps can occur anywhere and in anyone; however, leg cramps are especially common in older people. Quinine is a medicine which has been used to treat cramps for many years. There is conflicting evidence for its ability to reduce cramps. Quinine can cause serious, even fatal adverse events, especially in overdosage.

 
Study characteristics
This review includes 23 trials, with 1586 participants. The trials compared quinine or quinine-based medicines against inactive treatment (placebo) or other active treatments. We found no new studies when we searched the medical literature again and updated the review in 2014.
 

Key results and quality of the evidence
The risk of bias in the included trials varied considerably. All 23 trials claimed to be randomised, but many failed to clearly describe how participants were assigned to treatments. There is low quality evidence that quinine (200 mg to 500 mg daily) significantly reduces cramp number and cramp days and moderate quality evidence that quinine reduces cramp intensity. There is moderate quality evidence that there are more minor adverse events with quinine compared to placebo but no increase in major adverse events. However, there are reliable reports from other sources that an overdose of quinine can cause serious harm including death.
Low or moderate quality evidence shows there is no significant difference when comparing quinine to vitamin E or to a quinine-vitamin E mixture. There is evidence from one trial that theophylline combined with quinine improves cramps more than quinine alone. In a single trial there was no significant difference when comparing quinine to xylocaine injections.
More research is needed to clarify the best dose and duration of treatment, as well as alternatives to quinine for cramps.
The evidence is current to October 2014.

 

 

Authors' conclusions: 

There is low quality evidence that quinine (200 mg to 500 mg daily) significantly reduces cramp number and cramp days and moderate quality evidence that quinine reduces cramp intensity. There is moderate quality evidence that with use up to 60 days, the incidence of serious adverse events is not significantly greater than for placebo in the identified trials, but because serious adverse events can be rarely fatal, in some countries prescription of quinine is severely restricted.
Evidence from single trials suggests that theophylline combined with quinine improves cramps more than quinine alone, and the effects of xylocaine injections into gastrocnemius are not significantly different to quinine across all outcomes. Low or moderate quality evidence shows no significant difference between quinine and vitamin E or quinine and quinine-vitamin E mixture. Further research into these alternatives, as well other pharmacological and non-pharmacological treatments, is thus warranted.
There is no evidence to judge optimal dosage or duration of quinine treatment. Further studies using different dosages and measurement of serum quinine levels will allow a therapeutic range to be defined for muscle cramp. Because serious adverse events are not common, large population studies are required to more accurately inform incidence. Longer lengths of follow-up in future trials will help determine the duration of action following cessation of quinine as well as long-term adverse events. The search for new therapies, pharmacological and nonpharmacological, should continue and further trials should compare vitamin E, quinine-vitamin E combination, and quinine-theophylline mixture with quinine.