Study: One-third of initial prescriptions never filled

PHILADELPHIA — Medication nonadherence is common, but it may be reduced by lower drug costs and co-payments, as well as increased follow-up care, according to a study published earlier this week in the Annals of Internal Medicine. 

Primary nonadherence was defined as not filling an initial prescription within nine months. 

Overall, 31.3% of the 37,506 initial prescriptions written for the 15,961 patients were not filled, according to the study. Drugs in the upper quartile of cost were least likely to be filled, as were skin agents, gastrointestinal drugs and autonomic drugs, compared with anti-infectives.

An increase in adherence was associated with increasing patient age, elimination of prescription copayments for low-income groups and a greater proportion of all physician visits with the prescribing physician. 

One limitation of the study was that patients' rationale for choosing not to fill their prescriptions could not be measured, noted Robyn Tamblyn of McGill University, author of the study.