This study aims to evaluate changes in the durations of English National Health Service prescriptions, as indicated by the volumes of unit doses supplied between 1998 and 2009, and consider relevant policy implications.

Around the world, countries are seeking to manage the increase in medicines prescribing. In England, many primary care organisations, using limited supporting evidence of cost-effectiveness and clinical improvement, have sought to restrict the number of dosage units on a prescription to 28 days supply. This is based on a conviction that this reduces wastage costs.

Prescription Cost Analysis (PCA) statistics for England for the period January 1998 to December 2009 were used to analyse trends in the average number of unit doses (tablets or capsules) supplied per prescription for 11 drugs supplied in 34 different presentations.

The changes in prescription lengths observed between 1999 and 2009 ranged from +4.2% in the case of Amoxicillin 500 mg capsules to −41.3% in the case of Levothyroxine 50 μg tablets. All but four of the medicines selected showed statistically significant negative correlations (r > 0.8, P < 0.001) between the year of prescribing and the prescription length. If prescription lengths had been the same in 2009 as they were in 1999, then 33 million fewer prescription items would have been written for the preparations in this analysis. This shift across a range of medications suggests a generalised change in prescribing behaviour. The full balance of benefits and costs associated with this trend, as expressed via drug wastage avoided, patient (in)convenience experienced, professional time costs incurred or saved and positive or negative health outcome impacts, is not known. Although this study does not provide a definitive answer favouring prescription duration individualisation as opposed to standardisation, the available evidence indicates that policies that rigidly favour 28-day standard periods may require review.