Efficacy is not the same as effectiveness.1 A treatment is effective if it works in real life in non-ideal circumstances. In real life, medications will be used in doses and frequencies never studied and in patient groups never assessed in the trials. Drugs will be used in combination with other medications that have not been tested for interactions, and by people other than the patient - the ‘over the garden fence’ syndrome. Effectiveness cannot be measured in controlled trials, because the act of inclusion into a study is a distortion of usual practice.