Antidepressants prescribed for conditions other than depression

BMJ 1995;311:56-57 (1 July)

Letters

Antidepressants prescribed for conditions other than depression

EDITOR,--Susan S Jick and colleagues' study on the use of antidepressants,based on data from the VAMP database, and rates of suicide mayresult in more confusion than elucidation.¹ It is not clearwhether the initial hypothesis was that observed suicide rateswere evidence of failure to control depression, with consequentsuicide, or that the agents were themselves a causative factor.The distinction is important since one case deals with inefficacyand the other with an adverse reaction. No data are providedon the suicide rate in the British population, in all the patientson the database, or in a comparative group of patients. Riskfactors are compared between patients who have successfullycommitted suicide and a group who have unsuccessfully attemptedsuicide, even though they may have tried on many occasions.

The analyses of relative risk leave unaddressed a major confoundingfactor--namely, the numerous non-depressive conditions for whichthese agents are used. The IMS MediPlus database shows thatabout a fifth of prescriptions for selective serotonin reuptakeinhibitors are for diagnoses other than depression; for amitriptylineand dothiepin the proportion is over a quarter. In the specialcase of imipramine, roughly 35% of its use is for disordersof micturition (44% for Tofranil). These are high proportions,and adjustment should be made for them in any assessment thatdifferentiates products in terms of relative risk unless theobjective was specifically to evaluate suicide as an adversereaction.

Data available to Jick and colleagues extended to only February1993 and so are now two years out of date. This is a seriousproblem, since the advent of selective serotonin reuptake inhibitorshas radically altered prescribing patterns. Jick and colleaguesreport a ratio of dothiepin to fluoxetine of 6.3:1 (number ofpatients treated), whereas, for the last quarter of 1994, MediPlusdata show a ratio of 1.6:1. The ratio of dothiepin to all selectiveserotonin reuptake inhbitors was 0.86:1, making the inhibitorsthe most commonly used antidepressants in Britain. Jick andcolleagues report an apparent increase in risk attributed tofluoxetine, which, in the light of the greatly increased prescribingof selective serotonin reuptake inhibitors since the cut offpoint of their data, could be important. Absence of informationon comedication creates uncertainties, since many patients wouldhave been taking several drugs. MediPlus data confirm that sleepdisturbances are common in depressed patients and that benzodiazepinesare commonly prescribed to such patients: of 57000 patientstaking antidepressants, 28% were also prescribed either temazepamor diazepam. The earlier data should be reassessed in the lightof prevailing prescribing patterns.