Because quinine is commonly prescribed to treat leg cramps, researchers looked at the number of new quinine prescriptions for adults over 50 years of age in British Columbia, Canada, from Dec. 1, 2001 to Oct. 31, 2007. There were 31 339 people, of whom 61% were female, who began taking quinine during the 6-year study period. The researchers then looked at the frequency of Google searches from the United States and Australia for leg cramps.
They found that prescriptions for quinine peaked in British Columbia in July as did Google searches for leg cramps. In Australia, where mid-summer is in January, Google Trends data indicated a similar peak for leg cramp searches. There was no observed seasonality for search terms for back pain, kidney stones, migraines, acne or panic attacks.
“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,” writes Dr. Scott Garrison, Faculty of Medicine, University of Alberta, Edmonton, and the Centre for Hip Health and Mobility, University of British Columbia, Vancouver, with coauthors.
These findings could have implications for clinical practice.
“In countries where quinine is still in widespread use as prophylaxis 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,” suggest the authors.
In a related commentary, Dr. David Hogan, University of Calgary, writes that quinine sulfate, although widely used in Canada to treat nocturnal leg cramps, is not recommended for routine treatment because of safety concerns. Clinicians should first prescribe a 4-week course of quinine to determine if it works and encourage patients to try stopping the drug periodically to minimize use.
“The merit of a ‘quinine holiday’ during the colder months, as suggested by Garrison and colleagues, becomes moot if patients are not prescribed the agent in the first place or are periodically advised to try stopping it,” he writes.
Study: Seasonal effects on the occurrence of nocturnal leg cramps: a prospective cohort study, Scott R. Garrison MD PhD, Colin R. Dormuth ScD, Richard L. Morrow MA, Greg A. Carney BSc, Karim M. Khan MD PhD, CMAJ, DOI:10.1503/cmaj.140497, published 26 January 2015.
Commentary: Quinine: not a safe drug for treating nocturnal leg cramps, David B. Hogan MD, CMAJ, DOI:10.1503/cmaj.150044, published 26 January 2015.