Refill non-adherence to repeat prescriptions leads to treatment gaps or to high extra costs.

Objective: To determine the nature and extent of undersupply and the economic consequences of oversupply of medication among non-adherent patients.

Methods: This study used copies of repeat prescriptions (= multiple dispensations), collected during 1 week in 2002 at 16 Swedish community pharmacies. For patients with a refill adherence below 80%, treatment gaps were defined as the number of days they had no drug available. The cost of drug oversupply (i.e., refill adherence > 120%) was calculated from the prices of the drug packages dispensed.

Results: The number of collected repeat prescriptions was 3,636. The median of treatment gaps among patients with a refill adherence below 80% was 53 days per 90-100 days treatment period and the corresponding median for oversupply was 40 days. The cost of oversupply for exempt patients (i.e., patients who have paid 1,800 SEK (Euro 196; US$ 243) per year for medicines) was 32,000 SEK (Euro 3,500; US$ 4,300) higher than for non-exempt patients. An extrapolation to all Sweden indicates that exemption from charges leads to an additional oversupply of about 142 million SEK (Euro 15 million; US$ 19 million) per year above that of non-exempt patients.

Conclusion: Both undersupply and oversupply of prescribed medicines are common in Sweden. Patients with a refill adherence below 80% seem to have less than half of the prescribed treatment available. Oversupply or drug stockpiling occurs more frequently among exempt than among non-exempt patients, and this oversupply leads to high unnecessary costs.