GPs should not be deterred from prescribing quinine

EDITOR,—In their paper on the prescribing of quinine and drugs that induce cramp the authors seem to be trying to convey three messages, all in my opinion fallacious.1 One is that quinine is of doubtful efficacy in nocturnal cramps. Since Man-Son-Hing and Wells found a positive result for the drug in all of the six perfectly designed clinical trials that they analysed in their meta-analysis,2 I wonder what grounds the authors have for maintaining that “controversy surrounds its efficacy.”

The second message is that 53% of the patients in the practices investigated were also taking drugs “known to be associated with cramps” (nifedipine, cimetidine, salbutamol, terbutaline, and diuretics in general) and that the dose of these should be modified or the drug stopped. Cramps are an uncommon side effect of all of these drugs except salbutamol (when taken orally) and diuretics, and when they occur they are not solely nocturnal. It is certainly good practice to try to modify the dose of diuretic when cramps occur, though, interestingly, in one of the less than perfect trials (by Kaji et al) cited by Man-Son-Hing and Wells, when quinine was given to patients receiving haemodialysis it proved particularly effective and trouble free. The other drugs quoted are usually given for good indications, and to suggest that they are responsible for the cramps in a considerable proportion of the 53% of patients is guesswork.

The third message, and the most extraordinary, is that quinine is expensive and usually prescribed in practices where the general practitioners are “high cost, high volume” prescribers. There can be several reasons why some practices fit this description. For instance, they may have a high proportion of very young and very old patients; it is elderly patients who most often need quinine. The basic cost of a 300 mg quinine sulphate tablet is about 4p, so four weeks' supply at the usual dose of one tablet at bedtime costs £1.12. Few patients tortured by night cramps would grudge the NHS spending this sum.

Finally, the risk of ill effects from a nightly dose of 300 mg is extremely small. In the serious cases of toxicity described by Bateman and Dyson (cited by the authors) the patients had taken amounts measured in grams, not milligrams, and never less than six times the dose prescribed.3