Adrenergic neuron blockers
There are various labeled uses of adrenergic neurone blockers that are approved by the Food and Drug Administration (FDA), alongside some off-label uses.
[1] FDA-approved uses of these drugs include treating conditions like benign prostatic hyperplasia, hypertension, pheochromocytoma, extravasation management, and reversal of local anesthesia.
[1] Each agent has its own off-label uses, some examples include Tamsulosin for urinary disorders, Prazosin for post-traumatic stress disorder-related nightmares and Raynaud phenomenon, Phentolamine for hypertensive crisis and extravasation of vasopressors, and Phenoxybenzamine for neurogenic bladder and prostate obstruction.
[5] Alpha 1 blockers prevent smooth muscle contraction by inhibiting the downstream activation of Gq-type G-protein coupled receptors.
[1] By inhibiting this activation, alpha 1 blockers prevent the increase in intracellular calcium concentration and subsequent smooth muscle contraction.
[7] Alpha 1 receptor blockade, which results in vascular smooth muscle relaxation and consequent vasodilation, is the cause of hypotension.
[7] The occurrence of greater release of norepinephrine when numerous alpha 2 receptors are antagonised is what causes the remaining side effects.
[7] Due to their influence on the autonomic response to systemic changes, including a sudden drop in blood pressure, selective alpha 1 blockers can have adverse effects.
[7] The first-dose reaction can also result in tachycardia and orthostatic hypotension, which is characterised by a feeling of extreme dizziness that gets worse with an upright posture.
[10] For examples, certain non-selective beta blockers, such as carvedilol, can cause edema, and sotalol can block potassium channels in the heart, leading to QT prolongation and an increased risk of torsades de pointes.
[11] Selective beta 1 blockers have been shown to have an array of cardiac common side effects, comprising bradycardia, reduced exercise tolerance, hypotension, atrioventricular block, and heart failure.
[12] Additionally, beta 1 blockers can mask hypoglycaemia-induced tachycardia in diabetic patients, potentially leading to hypoglycaemic unawareness and subsequent complications if hypoglycaemia is not treated timely.
[5] Other possible adverse effects include the Raynaud phenomenon, hypoglycaemia during exercise, muscle cramps, an increase in airway resistance and symptoms related to bradycardia.
[3] Beta 1 blockers are contraindicated in people with complete or second-degree heart block or recent history of fluid retention without using diuretics.
[4] Patients with asthma or chronic obstructive pulmonary disease should refrain from using beta 2 blockers since they can cause bronchoconstriction, exacerbating the conditions.
