Medicine

Difference Between Alpha Blockers and Beta Blockers

Main difference

The main difference between alpha blockers and beta blockers is that alpha blockers occupy alpha receptors, thereby inhibiting all pharmacological actions of alpha receptor agonists, while beta blockers occupy beta receptors, thus inhibiting all pharmacological actions. of beta receptor agonists.

Alpha Blockers vs. Beta Blockers

Alpha blockers block all actions of alpha receptor agonists, while beta blockers block all actions of beta receptor agonists. Alpha-blockers inhibit vasoconstriction caused by endogenous catecholamines by relaxing some muscles, thus helping to keep blood vessels permanently open, while beta-blockers dilate blood vessels by causing vascular smooth muscle dilation, and some third-party beta-blockers generation also cause vasodilation. The drop in blood pressure induced by alpha-blockers is opposed by baroreceptors leading to an increase in blood pressure, while no such phenomenon is seen with beta-blockers. Alpha-blockers never act as “inverse agonists” , on the other hand, beta-blockers show the property of “inverse agonists”. Alpha-blockers keep the hormones norepinephrine or noradrenaline in place by causing smoother blood flow through open veins.

Alpha-blockers are used in the preoperative treatment of patients with pheochromocytoma, although their use is controversial, while beta-blockers are not used for this purpose. Alpha-blockers do not influence bronchial smooth muscles, while beta-blockers such as propranolol have a bronchial smooth muscle constriction property that is not significant in normal individuals, but is life-threatening in COPD patients due to induction of bronchoconstriction. Alpha blockers reduce resistance to urine flow, while beta blockers do not.

Comparison chart

alpha blockers beta blockers
Alpha blockers inhibit the pharmacological actions of alpha receptor agonists by blocking alpha receptors. Beta blockers inhibit the pharmacological actions of beta receptor agonists by blocking beta receptors.
Subtypes
Selective alpha-1 blockers (parazosin)
Selective alpha-2 blockers (yohimbine)
Non-selective alpha blockers (phentolamine)
Selective beta-1 blockers (metoprolol)
Selective beta-2 blockers (Albuterol)
Non-selective beta-blockers (propranolol)
Chronotropic and ionotropic effect
Alpha-blockers have no chronotropic or ionotropic effect. Beta blockers have a negative chronotropic and ionotropic effect.
Effect on peripheral resistance
Alpha blockers decrease peripheral vascular resistance. Long-term use of beta-blockers leads to a decrease in peripheral vascular resistance.
Role in blood glucose level
Alpha blockers have a role in lowering blood glucose levels. Beta-blockers lower the level of insulin even when the blood glucose level is high.
Use in heart failure and angina
Alpha-blockers are of no use in heart failure and angina pectoris. Beta blockers are used in heart failure and angina.
Adverse effects
Dizziness, postural hypotension, nasal congestion, reflex tachycardia, fluid retention Dizziness, cold hands and feet, headache, dry mouth, dry skin, upset stomach, diarrhea, or constipation.
therapeutic uses
Hypertension, pheochromocytoma, congestive heart failure, benign prostatic hyperplasia, erectile dysfunction, Raynaud’s syndrome, s Angina, heart attack, heart failure, atrial fibrillation, migraine

What are alpha blockers?

Alpha blockers, also called alpha antagonists, are drugs that act on the alpha receptors (Gq, coupled to Gi) of the sympathetic system and block the actions carried out by alpha agonists on these receptors (those drugs that act on and activate alpha receptors). The interaction of alpha blockers with alpha receptors can be reversible or irreversible. Reversible alpha-blockers are drugs that dissociate from receptors in the presence of high concentrations of alpha agonists, eg, phentolamine and prazosin. Irreversible alpha-blockers do not dissociate from receptors even in the presence of high concentrations of alpha-receptor agonists, eg, phenoxybenzamine. The effects of irreversible alpha-blockers may persist for a prolonged period even after the drug has been eliminated from the plasma. Some alpha blockers act specifically on alpha-1 receptors and are called alpha-1 blockers, for example prazosin. Some alpha blockers act specifically on alpha-2 receptors and are called alpha-2 blockers, for example yohimbine. Some alpha-blockers act on both receptors and are called non-selective alpha-blockers, for example phentolamine. Some drugs that block alpha receptors and also act on some other receptors are Indoramin, Ketanserin, Urapidil, neuroleptic drugs (chlorpromazine, haloperidol, phenothiazine and butyrophenones). The main therapeutic use of alpha-blockers is the treatment of hypertension, prostatic hyperplasia, pheochromocytoma, and they are also effective for erectile dysfunction. Some alpha-blockers act on both receptors and are called non-selective alpha-blockers, for example phentolamine. Some drugs that block alpha receptors and also act on some other receptors are Indoramin, Ketanserin, Urapidil, neuroleptic drugs (chlorpromazine, haloperidol, phenothiazine and butyrophenones). The main therapeutic use of alpha-blockers is the treatment of hypertension, prostatic hyperplasia, pheochromocytoma, and they are also effective for erectile dysfunction. Some alpha-blockers act on both receptors and are called non-selective alpha-blockers, for example phentolamine. Some drugs that block alpha receptors and also act on some other receptors are Indoramin, Ketanserin, Urapidil, neuroleptic drugs (chlorpromazine, haloperidol, phenothiazine and butyrophenones). The main therapeutic use of alpha-blockers is the treatment of hypertension, prostatic hyperplasia, pheochromocytoma, and they are also effective for erectile dysfunction.

What are Beta Blockers?

Beta blockers, also called beta antagonists, are drugs that act on the beta receptors of the sympathetic system and block the actions carried out by beta-agonists on these receptors (those drugs that act on beta receptors and activate them). Medications that block only Beta-1 receptors are called selective Beta-1 blockers, eg metoprolol, atenolol. Those drugs that block only Beta-2 receptors are called selective Beta-2 blockers, for example, those drugs that block beta 1 and beta 2 receptors are called non-selective beta receptors, for example propranolol. Some beta-blockers have the reverse agonism property |. Some beta blockers show the property of being a local anesthetic or membrane stabilizing activity.

Key differences

  1. Alpha blockers block the alpha receptors of the sympathetic system, while beta blockers block the beta receptors of the sympathetic system.
  2. Alpha blockers block Gi, Gq coupled receptors, while beta blockers block Gi and Gs coupled receptors.
  3. Alpha blockers do not have a chronotropic and ionotropic effect, on the other hand, beta blockers have a profound negative ionotropic and chronotropic effect.
  4. Alpha blockers are used to treat hypertension but postural hypotension is the adverse effect, on the other hand beta blockers treat hypertension but do not lead to postural hypotension.

Final Thought

Alpha and beta blockers are sympathetic nervous system blockers. Alpha and beta blockers find their main use in cardiovascular disorders and play a basic role in the treatment of cardiovascular diseases.

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