Monotoring adherence to prescribed medication in type 2 diabetic patients treated with sulfonylureas

Data on adherence to prescribed medication amongst diabetics are scarce. The purpose of this study was to collect information about the dynamics and patterns of compliance of elderly patients with type 2 diabetes mellitus on oral treatment by using different assessment techniques.

Adherence to prescribed sulfonylurea medication was prospectively assessed by Self-report (Sr), Pill count (Pc) and using a Medication Event Monitoring System (MEMS) over a period of 2 months in 19 elderly patients with type 2 diabetes mellitus. A pressure-activated microprocessor allowing the registration of each opening is located in the cap of the MEMS drug container. MEMS dosage adherence (MEMSd) was defined as the number of bottle openings divided by the number of doses prescribed), and MEMS regimen adherence (MEMSr) was defined as the percentage of days in which the dose regimen was taken as prescribed.

Adherence rates were 96.8 +/- 19.6% for Pc, 92.6 +/- 19.9% for MEMSd and 78.6 +/- 28.3% for MEMSr. Adherence rates for Pc were 103.8 +/- 10.9% in once daily regimens and 87.3 +/- 25.2% in bid/tid regimens (p = 0.0686). MEMSd was 101.0 +/- 4.8% in once daily regimens versus 81.0% +/- 26.8% in bid/tid regimens (p = 0.0255). MEMSr was 93.6 +/- 5.7% in once daily regimens versus only 57.8 +/- 34.1% in bid/tid regimens (p = 0.0031). Assessed by MEMSd as many as 42.1% of the participants had adherence rates greater than 100%. Over-compliance was found primarily in once daily regimens.

Adherence rates varied with different assessment techniques. Adherence rates were far from optimal. Once daily dosage led to significantly better adherence rates than two or three times daily regimens. However, over-compliance was surprisingly high and occurred more frequently on a once daily regimen.