The Mode of Action of Morphine Upon the Intestine

For more than sixty years differing views have been held about the action of morphine upon the intestine.The evidence was reviewed in detail in a recent paper (Vaughan Williams and Streeten, 1950), in which a new method of measuring intestinal propulsion was employed to demonstrate the relative potencies of analgesics on the activity of the bowel.Pethidine and amidone were found to be less active than morphine in retarding intestinal transport, in the ratio 75: 2.5: 1, the figures representing the number of molecules of active base of pethidine and amidone required to produce the same effect as one molecule of morphine base.In the same paper an explanation of the mode of action of morphine was offered, which resolved the apparent conflicts between the conclusions drawn by different workers employing a variety of methods.Further evidence is presented here which supports this explanation.Many people have shown that morphine causes an increase of intestinal " tone ";