No. 40: Jul-Aug 1985
The toxicities of many commonly used anticancer drugs depend upon when they are administered during the day. This phenomenon occurs in humans and other animals. The effect is not trivial but "profound."
(Hrushesky, W.J.M.; "Circadian Timing of Chemotherapy," Science, 228:73, 1985.)
Comment. This "profound" effect should, by extrapolation, also apply to drug potency, the workings of the immune system, and all biochemical reactions. The location of and reason for the circadian clock are matters of conjecture.