Promethazine was the first phenothiazine derivative to be successfully employed in combination with small doses of other agents for the management of labor.1,2 Similar application of related compounds followed. It was soon apparent that the addition of an appropriate phenothiazine derivative to the predelivery regimen reduced the total amount of narcotic required and attained a desirable quiescence and relaxation in the patient. The communication by Powe and co-workers in this issue of The Journal (p. 290) reports the results of a doubleblind comparative study. In order to minimize the number of variables which hamper the accurate evaluation of analgesic effect, a large series of patients (520) were randomly divided into 3 treatment groups.
Since clinical judgment is inherently subjective, it is important to design clinical trials of new drugs and the further evaluation of "accepted" forms of treatment in such a way that bias due to foreknowledge will be