Relationships between prescription and non-prescription drug use in an elderly population.

This paper explores, at an epidemiological level, the relationship between categories of over-the-counter (OTC) and prescribed (Rx) drugs in a community-resident elderly population. A total of 2818, randomly selected, older adults were interviewed at home about their use of prescribed and non-prescribed medication and other health-related factors. For comparative purposes OTC drugs were classified into 16 therapeutic groups-identical to those used by other researchers; prescribed drugs were classified into 45 British National Formulary (BNF) therapeutic sub-categories. Analyses revealed significant association between certain BNF categories and OTC categories, which may have a clinical explanation. These include a 3-fold increase (P<0.01) of OTC laxative use by those prescribed an antidepressant, and a 4-fold increase (P<0.001) in OTC antacid use among those prescribed oral corticosteroids. Our findings may indicate an attempt by older people to control side effects of prescription medicines with OTC preparations. This study, in part, supports the call by the Royal College of Physicians for further research to determine the effect of interactions (be they pharmacological, behavioural or otherwise) between OTC and prescribed medicines.