Summer Was Nighttime Leg Cramp Season

Quinine prescriptions for nighttime leg cramps spiked in the summer

(RxWiki News) Like Christmas and professional sports, nighttime leg cramps apparently have a season.

The authors of a new study found that quinine was prescribed more often in the summer than in other seasons. Quinine (brand name Qualaquin) is commonly used for leg cramps. Internet searches regarding leg cramps in the US and Australia also increased in summer months.

Although this study identified a seasonal trend in leg cramps, it did not determine why they were more frequent in the summer.

"Although there are anecdotal reports of pregnancy-associated rest cramps being worse in summer, these findings establish the phenomenon of seasonality in rest cramps in the general population,” said lead study author Scott R. Garrison, MD, PhD, of the University of Alberta in Edmonton, Canada, in a press release.

Nocturnal leg cramps are painful muscle spasms that occur at night. They can wake people from a sound sleep. Past research has found that these cramps may originate in the nerves, but their actual cause is unknown.

Pregnant women often report that leg cramps are more common during the summer months, these researchers said. Dr. Garrison and team wanted to confirm whether this finding was the norm for the general population as well.

They began by collecting data on new prescriptions for quinine written for people older than 50 from December 2001 to October 2007.

Dr. Garrison and colleagues found that prescriptions for quinine peaked during summer months — July in British Colombia and January in Australia. The seasons are reversed in the southern hemisphere, with summer occurring in December, January and February.

New prescriptions for quinine roughly doubled in the summer months, Dr. Garrison and team found.

Google searches on the subject of leg cramps followed the same seasonal pattern.

Dr. Garrison and team noted that routine quinine use may have some dangerous side effects. These are often rare but include vomiting, cold sweats, confusion, raised heart rate and trouble breathing, among others.

"In countries where quinine is still in widespread use as [a preventive measure] for nocturnal leg cramps despite safety warnings (e.g., Canada and the United Kingdom), physicians may choose to counsel patients to take a 'quinine holiday' during the 6 colder months of the year," Dr. Garrison and colleagues wrote.

Quinine is not approved by the US Food and Drug Administration for leg cramps. However, doctors often use it for that purpose because many have found it to be effective.

This study was published online Jan. 26 in the Canadian Medical Association Journal.

A grant to the Therapeutics Initiative’s Pharmacoepidemiology Working Group funded this research. Dr. Garrison received a Doctoral Research Award from the Canadian Institutes of Health Research (CIHR). Study author Dr. Karim M. Khan received a CIHR Emerging Team Grant. Study author Richard L. Morrow received a grant from the Therapeutics Initiative’s Pharmacoepidemiology Working Group from the British Columbia Ministry of Health.

Review Date: 
January 25, 2015