Prescribing of quinine and cramp inducing drugs in general practice

Patients, methods, and results

By using the Scottish prescribing analysis database provided by the pharmacy practice division in Edinburgh we established the quantity of quinine prescribed by the 221 practices operating within the Greater Glasgow Health Board conurbation. The top 5% of quinine prescribing practices had their overall prescribing reviewed in terms of the average cost per patient and number of prescription items issued per 100 patients and were compared with practices in the Greater Glasgow Health Board as a whole. Permission was sought from a sample of three of these practices (eight general practitioners) to access individual case notes of those patients prescribed quinine. Details of age, sex, and treatment histories at the time of diagnosis of leg cramps were obtained for some 70 patients.

During 1992 only 11 (5%) of the 221 practices in the Greater Glasgow Health Board did not prescribe quinine. The median number of tablets dispensed per 1000 patients a year was 1770 (table). Of the 14 practices prescribing more than 3500 tablets per 1000 patients, two closed and the remaining 12 formed the basis for this study.

Of the 12 practices, six had average annual prescribing costs of pounds sterling75 or more per patient. Practices prescribing more than 90 individual items per 100 patients were considered high volume prescribers. Seven of the 12 high quinine prescribers were among this group of high volume prescribers. Three of the 12 practices had individual patient case notes accessed. Prescriptions for quinine were predominantly issued to women patients aged over 65. Of the 70 patients identified as receiving quinine, 37 (53%) were taking other agents known to be associated with leg cramps before a diagnosis of leg cramps was made.

Comment

In 1992 virtually all general practitioners in the Greater Glasgow Health Board prescribed quinine sulphate. Quinine is prescribed predominantly by practices that may be regarded as high cost, high volume prescribers with regard to the Greater Glasgow Health Board as a whole. Our study highlighted that most patients prescribed quinine may have had another pharmacological cause for their leg cramps. A review of the need for and dosage of current drugs may be all that is required to alleviate the problem.

Controversy surrounds the efficacy of quinine in the treatment of nocturnal leg cramps. A recent metaanalysis concluded that quinine was effective for this condition.4 The authors, however, did not fully explore publication bias as a possible problem when interpreting their findings and the original trials did not investigate other pharmacological causes for the leg cramps in study subjects. Only if other cramp inducing agents cannot safely be stopped might a trial of quinine be indicated.