Results: The formal steps to obtain informed consent were usually carried out. Participants were
aware of the purpose of the trial and the right to discontinue participation, but only 23% knewthat
treatment was randomly allocated, 57% knew they might receive a placebo, and 42% was aware
that adverse effects could occur. Patients who had read the information sheet had better
knowledge ofmost aspects, except for the risk of adverse effects. The investigators considered that
compensation, insurance coverage, possibility of receiving a placebo, and treatment allocation
were the least important aspects of the trial when informing candidates for participation.
Conclusions: Although the formal steps for obtaining informed consentwere usually carried out, a
relevant percentage of patients included in clinical trials were unaware of important aspects of
their participation. Patients showed more limited knowledge about the same points that
investigators considered less important when informing potential participants. Deferring
signature on the consent form and encouraging reading of the information sheet may improve
participants' knowledge about clinical trials.