Pseudoephedrine is alpha and beta agonist used to treat nasal and sinus congestion as well as allergic rhinitis. It is in many cold and sinus medicines as well as allergy medicine. Pseudoephedrine's mechanism of action mainly occurs in the nose and sinuses. It primarily activates alpha adrenergic receptor 1A or 2A. Pseudoephedrine also inhibits sodium dependent noradrenaline receptors which prevents the reuptake of norepinephrine into the presynaptic neuron. This causes norepinephrine to accumulate in the synapse which also activates alpha adrenergic receptors. These receptors then activate the Gq protein cascade. This activates Phospolipase C which catalyzes Phosphatidylinositol 4,5-bisphosphate into Inositol 1,4,5-trisphosphate and Diacylglycerol. Diacylglycerol activates protain kinase C which activates the voltage-dependent calcium channel, allowing calcium to enter the cell. Inositol 1,4,5-trisphosphate activates Inositol 1,4,5-trisphosphate receptor on the sarcoplasmic reticulum which also allows calcium to enter the cell from the sarcoplasmic reticulum. This high concentration of calcium in the cytosol attaches to calmodulin which activates Myosin light chain kinase. This enzyme catalyzes Myosin light chain 3 into myosin LC-P which causes myosin to bind to actin and contract the muscle cell. The contraction of this smooth muscle causes the blood vessel to constrict. The contriction of blood vessels in the sinuses and nose lead to decongestion. Pseudophedrine also activates on beta receptors, and it inhibits sodium dependent dopamine and serotonin transporters, however not to the same effect or degree as it affects alpha receptors and the norepinephrine pathway.

Pseudoephedrine Pathway References