Introduction: Medications cannot be effective if they are not taken by patients. Many patients have difficulty following prescriptions.

Objective: To summarize the results of published studies of interventions to improve adherence with prescribed medications.
Methods: A systematic review of English language publications of randomized controlled trials of interventions to improve adherence with prescribed medications is being undertaken. Previous reviews are being updated using MEDLINE searches, culling of citations from bibliographies in articles on compliance, Science Citation Index tracing of key articles, articles in the authors' personal collections, and letters to experts. Articles have been judged to be of potential interest if they report original data concerning a randomized controlled trial of an intervention to improve adherence to prescribed medications of any sort. Studies must include at least one measure of medication adherence and at least one measure of treatment outcome, with at least 80% follow-up of each group studied and, for long-term treatments, at least 6 months follow-up.

Results: The review is in progress. Preliminary results show that the following interventions improve short-term adherence ( 2 wk): clear instructions, parenteral dosage forms, "reminder" pill packaging and calendars, and simplifying the drug regimen. Successful interventions for longer-term adherence include combinations of clear instructions; recalling non-attenders; self-monitoring; enhancement of social support; "contingency contracting"; rewards; and group discussion and supervised self-management. Most studies show some benefits for treatment outcomes. None of the interventions is self-sustaining.

Discussion: Patient adherence with medications can be enhanced, but not perfected, by a number of interventions within the purview of practitioners. It would be instructive to determine the extent of application of these interventions and their success in usual practice settings.