Variation in prescribing of hypnotics, anxiolytics and antidepressants between 61 general practices

Although the desirability of reducing prescribing of hypnotics and anxiolytics has long been recognized, variation between practices in patterns of psychotropic drug prescribing has received little attention; factors underlying such variation are poorly understood.

The study aimed to describe the extent of variation between general practices in the prescribing of hypnotics, anxiolytics and antidepressants; it also aimed to analyse the influence of measures of practice population and general practice and general practitioner characteristics on any variation in prescribing volumes.

Routinely collected prescribing data and practice population data, from April 1992 to March 1993, from all 61 practices in the Cambridge and Huntingdon Health Commission were analysed. Prescribing was measured as annual defined daily doses per 1000 practice population for each drug class. Data on variables relating to practice structure and general practitioner characteristics were obtained and analysed. Potentially influencing variables were investigated by multiple regression.

Between the highest and lowest prescribing practices there was an 11-fold difference, a 13-fold difference and an eightfold difference in the annual defined daily doses per 1000 practice population prescribed for hypnotics, for anxiolytics and for antidepressants, respectively. Strong positive correlations existed between volumes of prescribing of each drug class. The drugs prescribed in the greatest volumes were hypnotics. Practice population structure had some influence on psychotropic drug prescribing with high prescribing being associated with the proportions of temporary residents and women aged 65 years and over in the practice for all three classes of drug. Other factors, including presence of a practice counsellor, were not found to have a significant influence on psychotropic drug prescribing.

The degree of variation in prescribing volumes of psychotropic drugs between practices raises serious concerns. Further study is needed, but progress will be hampered until there is more clarity over the effectiveness and appropriateness of using these substances in the various illness, symptom and life-stress presentations seen in primary care.