ADRENERGIC RECEPTORS ANTAGONISTS

•Eye – Mydriasis (α₁)

•Vasoconstriction(α₁), decrease Salivation (α₁), and sweating

•Lungs – Bronchiodilation (β₂)

•Heart  -  Increase HR

    Increase AV Conduction           β₁

    Increase Contraction  

•Glycogenolysis (β₂), decrease motility (α,β), Increase Renin secretion, Urinary Retention (α₁)

•Uterine Relaxation - (β₂) 

 •These are also called sympatholytics-that reduces sympathetic  activities.

•Mostly used in the management of CVS diseases , glaucoma, migraine and urinary retention.

•Act by either reversibly and irreversibly attach to the receptors , preventing its activation by endogenous catecholamines.

•Divided into non selective and selective alpha blockers.

a.Non selective alpha blockers

•Agents that block alpha 1 and alpha 2 receptors are called non selective alpha receptors.

•Phenoxybenzamine and phentolamine are non competitive and competitive receptors respectively.

•Non selective .

•Formation of covalent bond.

•Block is irreversible, non competitive.

•Action lasts 24 hrs after single administration, reverse the action of epinephrine(alpha agonist).

•Decrease vascular resistance, increase blood flow to the skin ,mucosa , abdominal viscera and decrease blood pressure both in supine and standing position.

•Relax smooth muscles in UB and prostate.

•To treat pheochromocytoma-hypertensive episodes, to maintain blood pressure prior to surgical removal of tumor.

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•Rare tumor of adrenal gland tissue.

•It results in the release of too much epinephrine and nor - epinephrine, hormones that control heart rate, metabolism , and blood pressure.

•Young age – 1:1000.

•“Rule of 10” – 10 % malignant , 10 % extra adrenal , 10 % familial.

 •Abdominal pain , vomiting , Chest pain , irritability ,nervousness , pallor, palpitations, increase HR , severe headache , sweating , weight loss , hand tremor , insomnia and high BP. (Paroxysmal)

 

•Blood test for metanephrine

•Urine for metanephrine (24hrs sample)

•Blood for catecholamine's

•Glucose test

•Abdominal CT scan

•MRI of abdomen

•MIBG scintiscan (meta iodobenzyl guanidine)

•Adrenal biopsy

•Before surgery to stabilize blood pressure and pulse with medications.

•phenoxybenzamine ( α blocker) 10 – 20 mg orally / 6-8 hrs

•If tachycardia present – propranolol (β blocker) or combined α and β labetalol can be added .

•Surgery – removal of tumor  

 •Competitive receptor inhibitors .

•I/V administration-immediate on set, duration of action 10 – 15 minutes.

•I/M and S/C administration- onset of  action after 15 -20 minutes, duration of action 3-4 hours.

•Metabolize in liver , excreted through urine.

•Used to treat dermal necrosis, ischemia caused by extravasations or accidental injection of epinephrine and other  vasopressor  amines.

•Alfuzosine,doxazosine,prazosin,temulosin and terazosine.

•Given orally , highly bound with plasma proteins.

•Excreted in bile, urine and feces.

INDICATIONS

•To treat essential hypertension.

•To relax bladder, prostate smooth muscles to relieve urinary retention caused by BPH.

•Longer acting alpha 1 blocker,adminstred once a day to treat hypertension and BPH.

•Duration of  action is about 20 hours (terazocin )and 30 hours (Doxazosine).

•Hypotension (excessive vasodilatation).

•Dizziness , fainting , reflex tachycardia , palpitations and edema.

•All the clinically available  beta blockers are competitive antagonists.

•Non selective beta blockers act at both beta 1 and beta 2 receptors, cardio selective beta blockers, primarly block beta 1 receptors.

•These are nadolol,pindolol, propranalol, timolol.

•All the non - selective beta blockers can be administered orally but propranalol is given parenterally.

•Blocks both beta 1 and beta 2 receptors, non selective beta blockers.

•Actions on CVS.

1) Decrease cardiac output both negative inotropic and chronotropic effect.

2) Decrease SA and AV activity(direct action).

) Decrease oxygen consumption(useful to treat angina).

4) Effective in SV cardiac arrhythmia (beta   blockers).

5) Peripheral vaso constrictions(beta antagonist).

6) Broncho constrictions

7) Increase sodium retention.

8) Decrease glycogenlysis.

•Hypertension.

•Glaucoma.

•Migraine.

•Hyperthyroidism.

•Angina pectoris.

•MI .

1.Bronchospasm

2.Arrhythmias

Disturbance in metabolism glycogenolysis and decrease glucagon secretions.

•Selective beta 1 blockers-cardio selective.

•Decrease BP , increase exercise tolerance.

•Short duration of action.

•Given orally(acebutolol) to treat hypertension, cardiac arrhythmia(ventricular premature beats).

Atenolol

   given orally as well as parenterally, use to treat hypertension, angina, and acute MI.

Esomolol

   Given I/V , treat hypertension , acute SV tachycardia.

Carvedilol

•β1, β2 & α1 blockers

•Causes vasodilatation, decrease heart rate , decrease blood pressure in hypertensive patients.

•Increase COP in heart failure patient.

Labetolol

Non selective beta blockers and selective alpha 1 blockers to treat hypertension

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