Evaluation of Placebo Effect in Treatment of Asthma Based Onmetaanalysis of Trials on Selected Antiasthmatic Drugs

Introduction: Apart from the well-studied mechanisms of disease course modification, many therapeutic interventions, at leastin part, exert non-specific effects on patients. These effects can be measured by patient self-assessment or by technicalanalyses. The aim of the study was to assess the extent of placebo effect in the treatment of asthma based on revaluation ofresults of high-quality trials on inhaled antiasthmatic drugs and in the context of various applied investigative methods. Material and methods: A systematic search of the Medline database (using the Entrez Pubmed browser) was performedusing international drug names and English terms: inhaled, randomised, placebo-controlled. The aim of the search was toidentify trials on the efficacy of inhaled antiasthmatic drugs. Of the returned 454 studies, 41 were further included inmetaanalysis and assessed for correlations between drug effects and respective applied investigative methods. For com-parison, analogical analysis was performed for captopril, with 232 identified published studies of which 10 were included inthe metaanalysis. Results: The placebo effect in the treatment of asthma was significantly stronger (29%) as compared to the placebo effect ofcaptopril in patients treated for arterial hypertension (17%). The placebo effect was more prominent in studies applyingclinical (subjective) indicators of drug efficacy as compared to trials using objective (device-based) methods of drug effectmeasurement. Conclusions: The placebo effect is more prominent in treatment of asthma as compared to pharmacotherapy of arterialhypertension. Its extent depends on the applied methods of drug efficacy measurement and is often greater if only clinicalindicators are used. This phenomenon can lead to different interpretations of treatment goals in asthma as perceived by thephysician and the patient. This also points out the necessity of patient activation in taking control over his/her disease so asto achieve a better and more satisfying treatment result.