![]() The alpha-1 blockers are associated with the first-dose effect, which refers to the tachycardia response and orthostatic hypotension that caused by the systemic vasodilation at the initial administration of alpha-1 blockers. Mild body weight gain of 1–2 kg, which may be associated with secondary hyperaldosteronism, is also observed in some patients. Other adverse outcomes that are even more uncommon include headache, drowsiness, palpitations, urinary incontinence and priapism. With the vasodilation and smooth muscle relaxation caused by alpha-1 blockers, around 10 to 20% of patients present undesirable effects of asthenia(weakness), dizziness, faintness and syncope. The undesirable symptoms are mentioned in the following 'selective alpha-1 blocker' part. The common adverse effects of alpha blockers are due to the blockade of alpha-1 adrenergic receptors in tissue that requires high level of alpha adrenergic sympathetic input such as arterial resistance, vascular capacitance and the outflow tract of the urinary bladder. The adverse effects of non-selective alpha blockers are caused by the autonomic response to the systemic changes induced by the adrenergic blocking agents. Examples include non-selective beta blocker, which block both beta-1 receptor and beta-2 receptor as well. Some drugs, being non-selective, can exert actions on 2 or more different receptors. There are drugs that are approved by the Food and Drug Administration (FDA), whereas there are some off-label uses as well. As a result, it stops the body from producing the "fight-or-flight" responses. Īdrenergic blocking agents treat certain diseases through blocking the adrenergic receptor, preventing it from being activated by noradrenaline and epinephrine. Additionally, the heart rate and contractile force increase when SNS is activated, which may be harmful to cardiac function as it increases metabolic demand. ![]() These responses include vessel constriction in general vessels whereas there is vasodilation in vessels that supply skeletal muscles or in coronary vessels. These chemicals will act on adrenergic receptors, with subtypes Alpha-1, Alpha-2, Beta-1, Beta-2, Beta-3, which ultimately allow the body to trigger a "fight-or-flight" response to handle external stress. It triggers a series of responses after the body releases chemicals named noradrenaline and epinephrine. The sympathetic nervous system(SNS) is an autonomic nervous system that we cannot control by will. ![]() Adrenergic blocking agents are a class of drugs that exhibit its pharmacological action through inhibiting the action of the sympathetic nervous system in the body.
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