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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 ...
Adrenaline, also known as epinephrine, is a hormone and medication [10] [11] which is involved in regulating visceral functions (e.g., respiration). [ 10 ] [ 12 ] It appears as a white microcrystalline granule. [ 13 ]
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]
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]
This sympathetic response is to release epinephrine and norepinephrine, which results in peripheral vasoconstriction (reducing size of blood vessels) in order to conserve the circulating fluids for organs vital to survival (i.e. brain and heart). Peripheral vasoconstriction accounts for the cold extremities (hands and feet), increased heart ...
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.
Since β 2 adrenergic receptors can cause vascular smooth muscle dilation, beta blockers may cause some vasoconstriction. However, this effect tends to be small because the activity of β 2 receptors is overshadowed by the more dominant vasoconstricting α 1 receptors.
Like other β adrenergic agonists, they cause smooth muscle relaxation. β 2 adrenergic agonists' effects on smooth muscle cause dilation of bronchial passages, vasodilation in muscle and liver, relaxation of uterine muscle, and release of insulin. They are primarily used to treat asthma and other pulmonary disorders.