Six randomised, placebo-controlled, crossover trials were included (107 patients).
Compared with the placebo, in a 4-week treatment period, the use of quinine significantly reduced the number of nocturnal cramps by 8.83 (95% CI: 4.16, 13.49), and reduced the number of nights by 27.5% (95% CI: -30.6, -24.4). There was no significant change in the mean severity of leg cramps with quinine (-0.048 units on a three-point visual analogue scale, 95% CI -0.314, 0.218), compared with the placebo, or in cramp index (5.25 units, 95% CI: -10. 43, 20.93). Of the small minority that reported any side-effects at all, only one person experienced serious side-effects.