TEMPORAL VARIATION IN DRUG ABSORPTION -continued

Acute side effects of drugs are often corelated to initially high drug concentrations. It is possible to assume, therefore, that such side effects may occur more pronouncedly at that time of day at which Cmax values are highest and / or Tmax is shortest. At least with an immediate –release preparations of isosorbide-5-mononitrate orthostatic hypertension was most pronounced after morning dosing at which Tmax of isosorbide-5-mononitrate was significantly shorter than after evening dosing.

A diurnal rhythm in the absorption of glucose and water by isolated rat small intestine the absorption was 50-60% higher during night when the access to food was unrestricted. However when the feeding time was restricted to 6-9 hours, glucose and water absorption rates in the period 3-7 hours after withdrawal of food was almost as high as the rates observed at night time in the animals with unrestricted feeding. The changes in the absorption rates appear to be associated with feeding time and not with the pattern of illumination