Is a double-blind clinical trial really double-blind?
In a double-blind trial of meprobamate and placebo, carried out with 138 anxious neurotic outpatients, psychiatrists performed medication guesses after 2, 4, and 6 weeks of therapy. At the same time, physician and patient independently completed several improvement measures and the physician recorded the presence or absence of side reactions as spontaneously reported by the patient. The results may be summarized as follows: a) Clinical improvement and side effects often enable the physician to make reliable medication guesses and thus break the double-blind design in drug trials. b) Clinical improvement seems to exert the most important influence in determining physician medication guesses, at least with anti-anxiety drugs in studies of only 4 to 6 weeks duration. c) The correlation between side effects and medication guesses increases with the duration of therapy.