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When taken orally, phenylephrine has a threshold dose of about 50 mg to affect the cardiovascular system, a dose at which the drug decreases heart rate and slightly increases arterial blood pressure. [8] Additionally, an over-the-counter dose of 60 mg produces a slight increase in heart rate with no detectable changes in blood pressure. [8]
Examples of sympathomimetic effects include increases in heart rate, force of cardiac contraction, and blood pressure. [1] The primary endogenous agonists of the sympathetic nervous system are the catecholamines (i.e., epinephrine [adrenaline], norepinephrine [noradrenaline], and dopamine ), which function as both neurotransmitters and hormones .
Alpha adrenoreceptor ligands mimic the action of epinephrine and norepinephrine signaling in the heart, smooth muscle and central nervous system, with norepinephrine being the highest affinity. The activation of α 1 stimulates the membrane bound enzyme phospholipase C , and activation of α 2 inhibits the enzyme adenylate cyclase .
The concern goes beyond ineffectiveness; phenylephrine can come with side effects such as headaches, insomnia and nervousness. At higher doses, it can increase blood pressure.
Phenylephrine is found in a wide range of cold and flu medications, including Sudafed PE, Benadryl Allergy D Plus Sinus and Vicks DayQuil Cold and Flu Relief. Here’s what experts say are ...
Lusitropy or lucitropy is the rate of myocardial relaxation. The increase in cytosolic calcium of cardiomyocytes via increased uptake leads to increased myocardial contractility (positive inotropic effect), but the myocardial relaxation, or lusitropy, decreases.
The stakes are high, experts say, because a committee vote declaring phenylephrine ineffective as an oral decongestant could push the FDA to revoke the drug’s over-the-counter designation as ...
Increased heart rate and heart muscle contraction are associated with the β1 receptors; however, β 2 cause vasodilation in the myocardium. [citation needed] β3 receptors are mainly located in adipose tissue. [5] Activation of the β 3 receptors induces the metabolism of lipids. [6]