Effects of d-pseudoephedrine on tracheo-bronchial muscle and the cardiovascular system

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Abstract
The action of d-pseudoephedrine on bronchial smooth muscle, respiratory resistance and blood pressure was compared with that of l-ephedrine. Administration of dl-isoproterenol on isolated guinea pig tracheal muscle previously constricted with acetylcholine (ACh) or histamine (His) was the most effective and d-pseudoephedrine had the same effect as l-ephedrine. The relaxing effect of dl-isoproterenol, l-ephedrine or d-pseudoephedrine on ACh or His induced tracheal constriction was competitively antagonized by the pretreatment of propranolol. The i.v. or sublingual administration of d-pseudoephedrine on the increased respiratory resistance induced by His produced the same effect as l-ephedrine. The increase in blood pressure with d-pseudoephedrine was weaker than that of l-ephedrine. When l-ephedrine or d-pseudoephedrine was repeatedly injected into the same animal, signs of tachyphylaxis were observed. d-Pseudoephedrine, the main alkaloid of Ephedra helba, exhibited the same relaxing effect on bronchial smooth muscle as did l-ephedrine. The respiratory resistance increased by His was inhibited by the sublingual administration of d-pseudoephedrine and l-ephedrine.

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