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Epinephrine (adrenaline) reacts with both α- and β-adrenoreceptors, causing vasoconstriction and vasodilation, respectively. Although α receptors are less sensitive to epinephrine, when activated at pharmacologic doses, they override the vasodilation mediated by β-adrenoreceptors because there are more peripheral α 1 receptors than β ...
The epinephrine causes vasoconstriction which in turn reduces systemic distribution of the anesthetic as well as prolongs its action in addition to decreasing bleeding at the operating site. Lidocaine 2% with 1:100,000 adrenaline is the local anesthetic of choice in the treatment of pregnant women. [28]
The extent of vasoconstriction may be slight or severe depending on the substance or circumstance. Many vasoconstrictors also cause pupil dilation. Medications that cause vasoconstriction include: antihistamines, decongestants, and stimulants. Severe vasoconstriction may result in symptoms of intermittent claudication. [1]
Additionally, beta 1 blockers can affect beta 2 receptors, particularly at high doses, and hence should not be administered to patients with peripheral vascular disease or diabetes mellitus as they may cause vasoconstriction or a delayed hypoglycaemic response, respectively. [4]
Norepinephrine causes predominately vasoconstriction with a mild increase in heart rate, whereas epinephrine predominately causes an increase in heart rate with a small effect on the vascular tone; the combined effect results in an increase in blood pressure.
Epinephrine is also used as a bronchodilator for asthma if specific β 2 agonists are unavailable or ineffective. [39] Because of the high intrinsic efficacy (receptor binding ability) of epinephrine, high drug concentrations cause adverse side effects when treating asthma. The value of using nebulized epinephrine in acute asthma is unclear. [40]
Norepinephrine has higher affinity for the α 2 receptor than epinephrine does, and therefore relates less to the latter's functions. [16] Nonselective α 2 agonists include the antihypertensive drug clonidine, [16] which can be used to lower blood pressure and to reduce hot flashes associated with menopause.
The decrease in vasocongestion in post-menopausal women may require some women to use artificial sexual lubricant to avoid pain during sexual intercourse. If there is pain however, sexual drive is typically diminished or absent. Other forms of vasocongestion during human sexual activity include sex flush and the swelling of nipples in both men ...