Absorption kinetics of acetylsalicylic acid in gastrectomized patients

Abstract

Acetylsalicylic acid (ASA) is one of the oldest and most widely used medicinal agents today and its spectrum of therapeutic use is continually widening. Although many other drugs have been introduced during the last few years, ASA remains in a prominent position as the standard analgesic, antipyretic and anti-inflammatory drug of choice [1,2]. Gastrectomy consists of a partial or total surgical resection of the stomach, and the continuity of intestinal transit is re-established by means of the anastomosis of the remainder of the stomach with a gastro-duodenostomy (anastomosis Billroth Type I) or by a gastro-jejunostomy (Billroth Type II). When total gastrectomy is performed the intestinal transit continuity is re-established by directly connecting the esophagus with the jejunum (esophagus-jejunostomy)[13]. Orally administered ASA is rapidly and usually completely absorbed from the gastrointestinal tract. Absorption occurs by passive diffusion of unionized lipophilic molecules, partially from the stomach but mainly from the upper small intestine [4]. Gastrointestinal pH has a major influence on the rate of absorption of ASA by the two different mechanisms. At first low pH in the stomach provides optimum conditions for the absorption of undissociated ASA molecules. Then, as pH rises in the small intestine, the dissolution rate of ASA solid particles increases and is maximal at Ph8[4]. In Chile a large number of patients have undergone gastrectomy because of gastroduodenal disease. A clearer understanding of ASA absorption kinetics is therefore of great importance for the establishment of a safe an effective dose regimen for both acute and long term therapy of gastrectomized patients as well as subjects with normal gastrointestinal function [5].