Nocturnal leg cramps, that are cramps occurring at night, also known as rest cramps, are a painful involuntary muscle contraction that typically occur in the legs or feet during prolonged periods of rest and often interrupt sleep, says an article in the Canadian Medical Association Journal (CMAJ March 3, 2015).
Leg cramps are seasonal and roughly double between the winter lows and summer highs. It is not clear why there is such a seasonal occurrence. There is a midsummer peak and a midwinter dip.
Quinine sulfate at a dose of 200-300 mg at night has been used for many years to treat nocturnal leg cramps, says the article. Quinine is modestly effective. Other drugs were found to be either possibly effective (vitamin B complex, naftidrofuryl, calcium-channel blockers) or likely not effective (gabapentin, magnesium).
There is a long list of possible side effects that can occur with the usual dose of quinine. Some of the side effects are tinnitus (ringing in the ears), high-tone hearing loss, photophobia (visual intolerance to light) and other visual disturbances, just to mention a few.
Rarely, it can cause serous blood disorders (immune thrombocytopenic purpura and drug-mediated thrombotic microangiopathy). Overdose of quinine sulphate can cause serious and even fatal arrhythmias (irregular heart rhythm).
As of September 30, 2010, Health Canada had received 71 reports of serious adverse reactions suspected of being associated with quinine use (41 were either life threatening or required hospital admission), says the article. In 2009, the US Food and Drug Administration (FDA) explicitly noted an unfavourable risk-benefit ratio for quinine when used for leg cramps.
Although quinine is modestly effective, concerns regarding potential adverse effects have tempered enthusiasm about its use for nocturnal leg cramps, says the article. In fact practice guidelines for American neurologists on the symptomatic management of muscle cramps concluded that, although likely effective, quinine should be avoided for routine use because of the potential for toxic effects.
The author of the article says that quinine does not have Health Canada approval for the treatment of nocturnal leg cramps, yet it is widely used for this indication.
What else can be done for nocturnal leg cramps? Nightly calf and leg muscle stretching showed significant decrease in both the frequency and severity of leg cramps. The author does not suggest that quinine should be completely banned. It can be tried for short period. During the trial, patients should be closely monitored and the quinine stopped after four weeks if there is no benefit, says the article.
Patients continuing to take quinine after four weeks should be followed and advised periodically to try stopping it, says the author of the article.
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