Prescribing for multiple sclerosis patients in general practice: a case-control study

OBJECTIVES: To examine the prescribing patterns for multiple sclerosis (MS) patients resident in Wales by general practitioners (GPs), compared to an age, gender and GP surgery matched control population. METHODS: Anonymised data for 1996 were obtained for all patients from 24 GP practices in the all-Wales General Practice Morbidity Database (GPMD). This covered 220 538 patient years at risk for 1996. Cases were selected as those with a Read code of MS at some point from 1993 to 1996 (therefore had consulted the GP at least once during this time). The controls were age, gender and surgery matched patients randomly selected from the GPMD. RESULTS: A total of 216 cases were identified, giving a prevalence of 97.9 per 105. Cases were prescribed a mean of 15 drugs each in 1996 compared to eight drugs for controls (P < 0.0005). Compared with controls, MS patients were prescribed significantly more laxatives, diuretics, hypnotics and anxiolytics, antidepressants, antiepileptics (mainly carbamazepine), corticosteroids, oxybutynin, vitamin B12 and skeletal muscle relaxants (predominantly baclofen; P < 0.05). Certain 'MS specific' drugs were not frequently prescribed, such as cytotoxic immunosuppressants (two cases), amantadine (one case) and isoniazid (no cases). No case was prescribed medication for erectile dysfunction. Over 80% (44/53) of corticosteroid prescriptions for MS were for oral prednisolone. Over one-third (39%, 9/23) of cases prescribed a corticosteroid received a 'chronic' course. Over one-third (5/14) of courses of selective-serotonin re-uptake inhibitors (SSRI) for cases were identified as subtherapeutic. CONCLUSIONS: MS patients were high users of prescribed medicines, having almost twice as many prescriptions from the GP compared to controls. GP prescribing often reflected available evidence from published controlled trials, hence cytotoxic immunosuppressants, drugs for fatigue and tremor were seldom prescribed, whereas drugs such as oxybutynin and skeletal muscle relaxants were frequently prescribed. However, the increased use of certain drugs compared to controls such as diuretics, vitamin B12, hypnotics and anxiolytics were unsubstantiated in the literature. Furthermore, no published well-controlled clinical trials were found utilizing oral prednisolone or assessing the possible therapeutic benefit of chronic courses of corticosteroids in MS, both of which were prescribed by the GP. The absence of medication for sexual dysfunction (prelicensing of sildenafil), a reportedly common MS problem, was discussed. The relatively high incidence of subtherapeutic courses of SSRIs needs further investigation, given the increased incidence of depression and suicide associated with MS.