Methods in assessing drug compliance.

Methods and problems in assessing drug compliance are related to the selection of study sample and observation period as well as to methods used to measure patient behaviour in taking medications. Patients under treatment with a certain drug regimen are different from the patients for whom that regimen was originally prescribed. Medication compliance during short periods of time, such as 1-2 weeks before or after a visit to the clinic, is likely to be different from that found over longer periods of time. Several studies indicate that estimates by clinical staff are no more accurate than chance selections in determining medication compliance. Patient interviews have usually identified 25-50% of noncompliant patients, but interview data on spacing between doses seem to be more accurate. Pill counts are useful in assessing drug compliance, although compliance may sometimes be overestimated. Medication monitors provide more detailed information on patient behaviour in taking medications.