ON THE PHARMACOLOGY OF PHENYLISOPROPYLAMINE (BENZEDRINE)

1. Benzedrine (phenylisopropylamine) stimulated the central nervous system of anesthetized animals, as indicated by increase in rate and depth of respirations and by struggling and vocalization. 2. Benzedrine had a pressor action in dogs, cats and rabbits. Tachyphylaxis was marked. The pressor effect was moderately decreased by cocaine and ergotamine, respectively. 3. In low concentrations (10 –5 or less) benzedrine salts had either no effect on excised smooth muscles, (rabbits, guinea pigs) or inhibited the intestine (cat). 4. In high concentrations (10 –4 or higher) benzedrine caused contraction of all smooth muscles. A temporary inhibition of cat ileum and duodenum preceded the contraction produced by benzedrine. 5. The inhibition of cat ileum by benzedrine was prevented by atropine and decreased by nicotine. The contraction usually was not altered by atropine, but was decreased by nicotine. 6. Atropine and nicotine had no effect on the responses of rabbit tissues to benzedrine, but the contraction of guinea pig intestine was abolished by atropine. 7. Ergotamine abolished epinephrine action on cat duodenum but merely decreased (or left unaltered) the action of benzedrine. 8. Hydrastinine decreased or abolished the actions of epinephrine and of benzedrine. 9. Yohimbine contracted the intestine, but caused negligible alteration of the actions of epinephrine and of benzedrine.