Racepinephrine is a bronchodilator used to treat asthma. It can be found under the brand name Asthmanefrin and is orally inhaled to act on both alpha and beta adrenergic receptors. This drug has a rapid onset and short duration and acts as a smooth muscle relaxant and constrictor in different tissues. It is a beta-2 adrenergic receptor agonist which allows for the activation of adenylyl cyclase to relax the smooth muscle of the lungs, and it is also an alpha-1 adrenergic receptor agonist which causes smooth muscle constriction of arterioles. Constricting the pre capillary arterioles reduces the hydrostatic pressure and consequently bronchial mucosal edema. Racepinephrine is a racemic mixture consisting of d-Epinephrine and l-Epinephrine enantiomers. Epinephrine is a non-selective α- and β-adrenergic receptor agonist. Epinephrine also activates alpha 1A adrenergic receptors in blood vessels. Alpha 1A adrenergic receptor is coupled to Gq signaling pathway, therefore, activation of alpha 1A receptors leads to activation of protein kinase C and opening of IP3 receptors on the endoplasmic reticulum which increases intracellular calcium. Calcium is necessary for muscle contraction; thus, administration of epinephrine minimizes the vasodilation and increased the vascular permeability that occurs during anaphylaxis. Side effects of using racepinephrine may include blurred vision, chest pain, and difficulty speaking.

Racepinephrine A1-Adrenergic Vasoconstriction Pathway References