Circadian changes of the duration of action of local anaesthetic agents.

A statistically significant circadian rhythm of the duration of local anaesthesia produced by lidocaine and betoxycaine was found in both human skin and teeth. In adult subjects with diurnal activity and nocturnal rest the longest duration was found around 15.00 (3 p.m.) with a large peak-trough difference amounting to more than 100% of the 24 h mean. Such chronopharmacologic rhythm might be related to circadian rhythms in catecholamine secretion and/or in circadian changes of cell membrane properties.