[Diurnal differences in the effectiveness of an analgesic].

At different times of the day, the effect of an analgesic was systematically tested on healthy teeth by using a cold stimulus. The measure of the analgetic effect was the alteration of pain threshold measured by means of the minimum cold application time. In addition to the already known spontaneous variations in pain tolerance at the various times of the day, it was found that in the evening the effect of an analgesic is reduced and begins more slowly.