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A UK study has questioned the widely held assumption that polypharmacy is a marker of poor prescribing.

Researchers analysed data for 180,815 adults from 40 general practices in Scotland who regularly took several medications to treat chronic conditions. As expected, polypharmacy increased the likelihood of hospital admission. For example, 5.2 per cent of patients receiving one to three regular medications had unplanned admissions, compared to 10.3 per cent of patients receiving four to six medications and 24.8 per cent of patients receiving 10 or more medications.

After adjusting for potential confounders, people taking four to six medications were 25 per cent more likely to need an unplanned hospital admission than those taking one to three drugs. People taking at least 10 medications were more than three times more likely to need an unplanned admission.

However, in patients with several conditions, “only the most extreme levels of polypharmacy [were] associated with increased admissions”.

Among patients with at least six conditions, those taking four to six drugs were no more likely to have an unplanned admission than those taking one to three medications. Even patients taking at least 10 medications for at least six diseases were only 50 per cent more likely to be admitted.

The authors concluded that the study “provides powerful evidence that the number of regular medications is strongly associated with hospital admission”. However the number of conditions weakens this association. Therefore, “assumptions that polypharmacy is always hazardous and represents poor care should be tempered by clinical assessment of the conditions for which those drugs are prescribed”. (Br J Clin Pharmacol)