Adrenoceptor Antagonists Flashcards
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
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
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
Nonselective alpha blockers + noncompetitive/competitive
Phenoxybenzamine (noncompetitive)
Phentolamine (competitive)
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.
Phenoxybenzamine - Indication
Hypertensive episodes in pat with pheochromocytoma (used to control hypertension until surgery can be performed to remove tumor).
Phentolamine - MoA
Competetive adrenoceptor antagonist, produces vasodilation, decreases peripheral vascular resistance and decreases BP.
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.
Why is nonselective alpha adrenoceptor antagonists not useful in treating chronic hypertension?
Evoke reflex tachycardia and may cause dizziness, headache and nasal congestion.
Nonselective alpha adrenoceptor antagonists -Adverse Effects
Reflex tachycardia
Dizziness
Headache
Nasal congestion
Selective alpha adrenoceptor antagonists
Prazosin Doxazosin Terazosin Alfuzosin Silodosin Tamsulosin
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
Selective alpha adrenoceptor antagonists - Indication
Used to treat essential(primary) hypertension
Lower urinary tract symptoms associated with benign prostatic hyperplasia and other conditions.
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.
Prazosin, Doxazosin and Terazosin - Indication
Hypertension; Urinary symptoms caused by benign prostatic hyperplasia
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
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
