Sedative properties of simple analgesics.

1. An attempt has been made to assess under double blind conditions the sedative action of phenacetin, paracetamol, and aspirin by testing their ability to prolong sleep in the face of a rapidly filling bladder.2. The volume in the bladder on awakening was independent of the rate of urine formation.3. Although phenacetin prolonged sleep there was no corresponding increase in urine volume on awakening. Apparently phenacetin sensitized the bladder to the distending volume and reduced the rate of urine formation. It was unnecessary to postulate sedative action to explain the results.4. Paracetamol had no effect on the mean sleep interval or mean urine volume although the drug was not totally inactive since it increased the variance of the results for sleep interval and urine volume.5. Aspirin prolonged sleep interval, but this effect would be explained if it were an antidiuretic because there was no increase in urine volume on awakening.6. Apparently no sedative or hypnotic has been shown to increase the urine volume on awakening under similar conditions.