Adrenoceptor Antagonists Flashcards by Dane Schultz

Peripheral vascular resistance - Effects of alpha1 and beta 1 blockers

alpha1 blockers: reduced peripheral vascular resistance

beta1 blockers: slight increase in peripheral vascular resistance as a results of reflex vasoconstriction

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Cardiac output - Effects of alpha1 and beta 1 blockers

alpha1 blockers: increase CO by decreasing cardiac after load and aortic impedance to ventricular ejection of blood
beta1 blockers: reduce CO

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Mean arterial BP- Effects of alpha1 and beta 1 blockers

Kidneys - Effects of beta 1 blockers

Mean arterial BP: Both reduce

Kidneys: Reduces renin secretion –> reduces synthesis of angiotensin –> reduces NP

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Nonselective alpha blockers + noncompetitive/competitive

Phenoxybenzamine (noncompetitive)

Phentolamine (competitive)

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Phenoxybenzamine - MoA and Effect

Undergoes nonenzymatic chemical transformation to and active metabolite that forms a long-lasting covalent bond with alpha-adrenoceptors, resulting in noncompetetive receptor blockade.

Casues vasodilation –>Decreases vascular resistance and lowers both supine and standing BP.

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Phenoxybenzamine - Indication

Hypertensive episodes in pat with pheochromocytoma (used to control hypertension until surgery can be performed to remove tumor).

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Phentolamine - MoA

Competetive adrenoceptor antagonist, produces vasodilation, decreases peripheral vascular resistance and decreases BP.

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Phentolamine - Indication

Acute hypertensive episodes caused by adrenoreceptor agonists

Counteract local ischemia caused by accidental injection or extravasation (leakage from IV infusion) of epinephrine or other vasopressor amines.

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Why is nonselective alpha adrenoceptor antagonists not useful in treating chronic hypertension?

Evoke reflex tachycardia and may cause dizziness, headache and nasal congestion.

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Nonselective alpha adrenoceptor antagonists -Adverse Effects

Reflex tachycardia
Dizziness
Headache
Nasal congestion

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Selective alpha adrenoceptor antagonists

Prazosin
Doxazosin
Terazosin
Alfuzosin
Silodosin
Tamsulosin

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Selective alpha adrenoceptor antagonists - MoA

Selectivley block alpha1 adrenoceptors and relax vascular and other smooth muscles, including those of urinary bladder, urethra and prostate. Produce vasodilation and decrease BP.
Competitive alpha 1 adrenoceptor antagonists

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Selective alpha adrenoceptor antagonists - Indication

Used to treat essential(primary) hypertension

Lower urinary tract symptoms associated with benign prostatic hyperplasia and other conditions.

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Selective alpha adrenoceptor antagonists - Adverse effects

Less reflex tachycardia then Phentolamine and other nonselective α1-and α2-adrenoreceptors

Hypotension
Dizziness
Sedation
Small percentage of men have abnormal ejaculation.

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Prazosin, Doxazosin and Terazosin - Indication

Hypertension; Urinary symptoms caused by benign prostatic hyperplasia

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Which selective alpha-adrenoceptor antagonists are not used for treating hypertension but only symptoms of urinary outflow obstruction in men with benign prostate hyperplasia?

Alfuzosin, Silodosin, Tamsulosin

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Which selective alpha-adrenoceptor antagonists have higher incidence of adverse effects?

Doxazosin and Terazosin

Alfuzosin, Silodosin and Tamsulosin - MoA

Competetive alpha1 blocker.

Selectively block alpha1A-adrenoreceptors, which is the alpha1-receptor subtype that mediates contraction of the ureter and urinary bladder.

Nonselective beta-adrenoceptor antagonists - MoA

Block beta1-adrenoreceptors in the heart and other tissues

Block beta2-adrenoreceptors in blood vessels, lungs, and the liver

Competitvely block the effect of norepinephrine and other adrenoceptor agonists at beta1 and beta2 adrenoceptors.

They all decrease cardiac rate, output, AV node conduction and O2 demand and blood pressure

Nonselective beta-adrenoceptor antagonists - Adverse effects

Beta2-blockers in liver inhibit epinephrine stimulated glycogenolysis and can thereby reduce hepatic glucose output during hypoglycemia resulting from excessive insulin adm. –> tachycardia and sweating(early signs of hypoglycemia)

Beta2-blockers can cause adverse reaction in asthma patients, due to bronchoconstriction, these persons depend on endogenous epinephrine to prevent bronchospasm, so beta2-blockers should be used with caution.
–> rather beta1-blockers in these patients.

Decreased peripheral blood flow during exercise, and a risk of cold extremities

Nonselective beta-adrenoceptor antagonists

Nadolol
Pindolol
Propranolol
Timolol
Carteolol

Nadolol - MoA and Indication

beta1- and beta2-blocker

Hypertension
Angina pectoris
Migrane headache

Pindolol - MoA and Indication

beta1- and beta2-blocker with ISA and MSA

Hypertension

Propranolol - MoA an Indication

beta1- and beta2-blocker with MSA

Hypertension
Angina pectoris
Cardiac dysrhythmias 
Hypertrophic subaortic stenosis
Essential tremor
Migrane headache 
Acute thyrotoxicosis
Acute myocardial infaction
Pheochromocytoma

Timolol - MoA and Indication

beta1- and beta2-blocker Reduce intraocular pressure by decreased aqueous humor production Glaucoma Hypertension Acute myocardial infarction Migrane headace

Carteolol - MoA and Indication

beta1- and beta2-blocker Reduce intraocular pressure by decreased aqueous humor production Glaucoma Intraocular hypertension

Carteolol - Adverse effects

Temporary blurred vision | Temporary burning/stinging/itching/redness of the eye may occur.

Selective beta-Adrenoceptor antagonists

``` Acebutolol Atenolol Esmolol Betaxolol Bisoprolol Metaprolol Nebivolol ```

Acetbutolol - MoA and Indication

beta1 blocker with ISA(intrinsic sympathomimetic activity, partial agonist activity) and MSA(membrane stabilizing activity, local anesthetic activity) Hypertension; cardiac arrhythmias

Atenolol - MoA and Indication

b1-blocker Hypertension Angina pectoris Acute myocardial infarction

Esmolol - MoA and Indication

b1-blocker Hypertension and Supraventricular tachycardia when these occur during surgery and in other situations

Betaxolol - MoA and Indication

b1-blocker, decreases intraocular pressure Glaucoma

Bisoprolol - MoA and Indication

b1-blocker | Hypertension

Metoprolol - MoA and Indication

b1-blocker with MSA Hypertension Angina pectoris Acute myocardial infarction

Nebivolol - MoA and Indication

b1-blocker - Hypertension

alpha- and beta-Adrenoceptor antagonists

Carvedilol | Labetalol

Carvedilol - MoA and Effect

beta1- and beta2-blocker alpha1-blocker Decreases cardiac afterload, increases cardiac output in patients with heart failure. Antioxidant effects: Inhibition of lipid peroxidation in myocardial membranes Scavenging of free radicals Inhibition of neutrophil release of O2 Antiapoptotic properties that can prevent myocyte death and reduce infarct size in persons with myocardial ischemia. For these reasons, carvedilol has been called a “third-generation -blocker and neurohumoral antagonist”.

Carvedilol - Indication

Hypertension | Heart failure

Labetalol - MoA

beta1- and beta2-blocker with MSA alpha1-blocker, but more potent as a beta-blocker. Decreases heart rate and cardiac output as a result of blocking beta1-adrenoceptors Decreases peripheral vascular resistance as a result of alpha1-receptor blockade

Labetalol - Indication

Hypertension