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N-of-1 trials of quinine efficacy in skeletal muscle cramps of the leg.

Author(s): Woodfield R, Goodyear-Smith F, Arroll B

Affiliation(s): School of Pharmacy, University of Otago, Dunedin, New Zealand.

Publication date & source: 2005-03, Br J Gen Pract., 55(512):181-5.

Publication type: Clinical Trial; Meta-Analysis; Multicenter Study; Randomized Controlled Trial

BACKGROUND: Skeletal muscle cramps affect over a third of the ambulatory elderly population. Quinine is the established treatment, but there are safety concerns, and evidence for efficacy is conflicting. A recent meta-analysis established a small advantage for quinine, but identified the need for additional studies. N-of-1 trials compare two treatments, in a randomised, double-blind, multiple crossover study on a patient-by-patient basis. They have been used to compare treatments in osteoarthritis and may be suitable for determining the individual efficacy of quinine. AIM: To establish efficacy and safety of quinine sulphate use for the treatment of leg-muscle cramp. DESIGN OF STUDY: Double-blind, randomised series of n-of-1 controlled trials of quinine versus placebo for muscle cramps. SETTING: New Zealand general practices. METHOD: The participants were 13 general practice patients (six males; seven females; median age = 75 years) already prescribed quinine. Following a 2-week washout, each patient received three 4-week treatment blocks of quinine sulphate and matched placebo capsules with an individual, randomised crossover design. The main outcome measures were: patient diaries of cramp occurrence, duration and severity; capsule counts; and blood quinine levels in the final treatment block. RESULTS: Ten patients completed the trial. Three patients were identified for whom quinine was clearly beneficial (P <0.05), six showed non-significant benefit and one showed no benefit. All patients elected to continue quinine post-study. CONCLUSION: Series of n -of-1 studies differentiated patients whom quinine had statistically significant effects; those with trend towards effectiveness; those for whom quinine was probably not effective. Ideally n-of-1 trial should be performed when a patient is commenced on quinine. More cycles in n-of-1 studies of quinine may address issues of statistical power.

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