Effect of gastrointestinal transit on the bioavailability of orally administered drugs in rabbit

The effect of gastrointestinal [GI] transit rate on the absorption behavior of orally administered drug was investigated, using aqueous, oily and aqueous vehicles pretreated with propantheline, in rabbits and three-way crossover design. The absorption behavior was examined for sodium salicylate as a model drug since it is well absorbed from both the stomach and small intestine. The three bioavailability parameters, Tmax, Cmax and AUCO-24, that were obtained from the three different treatments, were compared. The results clarified that delay in the gastric emptying rate [GER], brought about by the oil or by propantheline, lowers the rate of absorption and enhances the extent of absorption of salicylates compared with the aqueous solution. The viscosity of the oil plays no significant role in the results obtained

Lack of sodium salicylate-induced enhancement of hepatic tryptophan pyrrolase in 5 day salicylate injected rats

Single administration of sodium salicylate at doses of 400 mg/kg increased hepatic holo-tryptophan pyrrolase activity but did not produce any effect an apotryptophan pyrrolase activity in rats. Repeated administration of the drug at doses of 100 mg/kg did not alter holo-enzyme activity but decreased apo and total enzyme activity in rats killed 24 hours later. Administration of 400 mg/kg sodium salicylate to 5 day, 100 mg/kg sodium salicylate injected rats did not increase holo or apo-tryptophan pyrrolase activity. Possible role of tryptophan pyrrolase in the sodium- salicylate induced changes of brain serotonin metabolism is discussed