Cyclopentamine is a sympathomimetic alkylamine, classified as a vasoconstrictor. Cyclopentamine was indicated in the past as an over-the-counter medication for use as a nasal decongestant, notably in Europe and Australia, but has now been largely discontinued possibly due to the availability, effectiveness, and safety of a structurally similar drug, propylhexedrine used for relief of congestion due to colds, common cold, hay fever, or other allergies. Cyclopentamine acts as a releasing agent of the catecholamine neurotransmitters norepinephrine (noradrenaline), epinephrine (adrenaline), and dopamine. Cyclopentamine effects on norepinephrine and epinephrine mediate its decongestant effects, while its effects on all three neurotransmitters are responsible for its stimulant properties. Cyclopentamine was acting as nonspecific spasmolytic, similar to papaverine, in the rabbit ileum. It was demonstrated that cyclopentamine was a very weak alpha-adrenergic receptor stimulant and a weak beta-adrenergic receptor blocker. Cyclopentamine also potentiated the auto-inhibition produced by high doses of isoproterenol and the effect lasted as long as the autoinhibition persisted. It was suggested that the blockade by both drugs was the result of a direct action on the beta receptors. When ingested orally in sufficient quantities, cyclopentamine produces similar effects to amphetamine, methamphetamine, and propylhexedrine.