Scientific background: Poor compliance or adherence in drug therapy can cause increased morbidity, mortality and enormous costs in the healthcare system (in Germany annually approximately 10 billion euros). Different methods are used for enhancing the compliance or adherence. Research questions: The evaluation addresses the questions about existence, efficacy, cost-benefit relation as well as ethical-social and juridical implications of strategies for enhancing compliance or adherence in drug therapy with concomitant improvements in treatment outcomes. Methods: A systematic literature search was conducted in the medical, also health economic relevant, literature databases in January 2007, beginning from 2002. Systematic reviews on the basis of (randomised controlled trials (RCT) concerning interventions to enhance compliance or adherence with regard to treatment outcomes as well as systematic reviews of health economic analyses were included in the evaluation. Additionally, it was also searched for publications which primarily considered ethical-social and juridical aspects of these interventions for the German context. Results: One systematic review with data for 57 RCT was included in the medical evaluation and one systematic review with data for six studies into the health economic evaluation. No publication primary concerning ethical-social or juridical implications could be identified. A significant positive effect on the treatment outcome was reported for 22 evaluated interventions. For many interventions the results can be classified as reliable: counseling with providing an information leaflet and compliance diary chart followed by phone consultation for helicobacter pylori positive patients, repeated counseling for patients with acute asthma symptoms, telephone calls to establish the level of compliance and to make recommendations based on that for the therapy of cardiovascular diseases, calls of an automated telephone system with phone counseling in problem cases for diabetics, different family based interventions including repeated family counseling, education and "culturally modified family therapy" in patients with schizophrenia, repeated "compliance therapy" sessions for patients with acute psychosis. For other interventions the results should be viewed with more concern (because of the poor methodical quality of the underlying studies). The effect size of the interventions can not be estimated from the available data. From the available data, no reliable results can be provided concerning the cost-benefit relation of these strategies. Discussion: Many of the reported studies had a poor reporting and methodological quality. The reliability of the conclusions of the studies is restricted because of methodical shortcomings. Efficacy and cost estimates determined in the health economic studies are not transferable to the current situation in Germany. It has been discussed recently that the compliance or adherence enhancing interventions can restrict the autonomy and the privacy of the patients. Conclusions: In drug therapy some compliance or adherence enhancing interventions with concomitant positive effect on the treatment outcome may be used. The cost-benefit relation of these interventions is to be estimated. Using these interventions the patient’s autonomy and privacy are to be restricted as few as possible
