Chronopharmacology of probucol in mice.

Mice were maintained under conditions of light from 7 a.m. to 7 p.m. and dark from 7 p.m. to 7 a.m. Probucol was given orally to these animals once daily at 10 a.m. or 10 p.m. for 7 days. Blood samples for serum cholesterol were obtained at 24 hours after the final dosage. Blood samples for plasma probucol were obtained just before and at 3, 6, 12, 24, 48, 72, 96 and 120 hours after the final dosage. The cholesterol lowering effect of the agent at 10 p.m. was greater than that at 10 a.m. Plasma probucol concentrations of the two trials did not differ at any observation point. These data suggest that the effect of probucol varies with its time of administration. This might not be caused by a time-dependent change in plasma probucol concentration.