Magnesium for the treatment of nocturnal leg cramps: a crossover randomized trial.
BACKGROUND
Nocturnal leg cramps are a common health problem in the ambulatory setting. Our objective was to evaluate the efficacy of magnesium in the treatment of nocturnal leg cramps.


METHODS
Our study was a crossover randomized double-blind placebo-controlled trial. We included patients from a large university-based ambulatory clinic in Buenos Aires, Argentina, with at least 6 cramps during the previous month. A total of 93 subjects took part in a 4-week washout period with placebo. Those who were still eligible (n = 45) were randomized to receive either (1) an oral dose of 900 mg magnesium citrate twice daily for 1 month, followed by a matching placebo for 1 month, or (2) the placebo first, followed by magnesium. Both groups had a 4-week washout period with placebo between each treatment month. Forty-two patients completed the 4-month study. The main outcome was the number of nocturnal leg cramps, and the secondary outcomes were duration, severity, and sleep disorders caused by those cramps.


RESULTS
There were no significant differences between magnesium and placebo in any of the evaluated outcomes. The mean number of cramps was 11.1 (standard deviation [SD] +/- 7.3) for placebo versus 11.8 (SD +/- 7.6) for magnesium (P = .59). We observed a significant period-effect bias: All patients improved over time regardless of the treatment sequence they received.


CONCLUSIONS
Magnesium was not effective for the treatment of nocturnal leg cramps. The period-effect bias probably occurred because of a combination of the natural history of this condition, a regression to the mean, and a true placebo effect.
Frusso
R
R
Unidad de Medicina Familiar y Preventiva, Hospital Italiano de Buenos Aires, Argentina.
Zárate
M
M
Augustovski
F
F
Rubinstein
A
A
D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D018592:Cross-Over Studies; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008274:Magnesium / Q000627:therapeutic use*; D008297:Male; D008875:Middle Aged; D009120:Muscle Cramp / Q000150:complications / Q000188:drug therapy*; D012893:Sleep Wake Disorders / Q000209:etiology; D016896:Treatment Outcome
D008274:Magnesium