A RANDOMIZED CLINICAL-TRIAL OF THE EFFECT OF INFORMED CONSENT ON THE ANALGESIC ACTIVITY OF PLACEBO AND NAPROXEN IN CANCER PAIN

To determine whether informed consent in a therapeutic trial modifies the analgesic effect of naproxen and placebo, we conducted a prospecti ve, randomised, single dose, placebo-controlled trial. Patients were r andomly selected to receive or not information concerning the study. A ll patients included were then given a single dose of naproxen and pla cebo according to a crossover, double-blind design. Forty-nine patient s with mild or moderate cancer pain which did not need narcotic analge sics entered the study. Twenty-five received both treatments without a ny information and constituted the uninformed group. Twenty-four had a complete information about the trial; six refused to participate. The 18 others constituted the informed-consent group. Visual analogue sca les of pain before and 30, 60, 120 and 180 min after the intake of nap roxen and placebo were recorded. As an analgesic, naproxen was more ef fective than placebo in both groups of patients (p = 0.001). For napro xen as well as for placebo, the analgesic effect was better in the inf ormed-consent group compared to the uninformed group (p = 0.012). The difference in therapeutic activity between naproxen and placebo was mo derately higher in the uninformed patients (p = 0.08). We concluded th at, in contrast with parallel studies, giving information in a crossov er, placebo-controlled trial may increase the apparent efficacy of bot h the tested agent and the placebo, and decrease the perceived differe nce between the two.