2-Adrenergic Blockers PDF

Adrenergic blockers Dr. Romany H Thabet, PhD Alpha- adrenergic antagonists: Therapeutic applications:  essential hypertension: by blocking alpha1 receptors on arterioles and veins  vasodilation  reversal of toxicity from alpha1 agonists  Benign prostatic hyperplasia: Block alpha1 recep...

Adrenergic blockers Dr. Romany H Thabet, PhD Alpha- adrenergic antagonists: Therapeutic applications:  essential hypertension: by blocking alpha1 receptors on arterioles and veins  vasodilation  reversal of toxicity from alpha1 agonists  Benign prostatic hyperplasia: Block alpha1 receptors  reduced contraction of smooth muscle in the bladder neck and prostatic capsule  Reduce urinary urgency Tamsulosin Alfuzosin Alpha- adrenergic antagonists: Therapeutic applications:  Pheochromocytoma: A catecholamine-secreting tumor e.g. phenoxybenzamine, phentolamine  Raynaud’s disease: Peripheral vascular disorder characterized by vasospasm in the toes and fingers  local sensation if cold and pain Alpha- adrenergic antagonists: Adverse effects:  orthostatic hypotension:  blockade of alpha receptors on veins reduced venous toneblood accumulate in veins when patient assumes erect position reduced return of blood to the heart reduced cardiac output  decrease BP  reduce blood flow to brain lightheadedness, dizziness Alpha- adrenergic antagonists: Adverse effects:  reflex tachycardia:  blockade of vascular alpha1 receptors vasodilation reduce BP baroreceptor initiate a reflex increase in heart rate via the ANS  Nasal congestion: dilate blood vessels in the nasal mucosa Alpha- adrenergic antagonists: Adverse effects:  Inhibition of ejaculation:  Blockade of alpha 1 receptors  Can cause impotence  Reversible when the alpha blocker is withdrawn  Can be a major reason for noncompliance change the medication Alpha- adrenergic antagonists: a. Prazosin:  selective blockade of alpha1- adrenergic receptors  hypertension: dilate arterioles and veins  relaxation of smooth muscle in bladder neck and prostatic capsule Alpha- adrenergic antagonists: a. Prazosin: Adverse effects:  orthostatic hypotension, reflex tachycardia, inhibition of ejaculation, and nasal congestion  first dose effect: 1% of patients lose consciousness 30-60 minutes after receiving their first dose result of sever postural hypotension minimize it by using small initial dose (1mg or less) beginning the treatment: avoid driving and other hazardous activity for 12-24 hours administer the initial dose at bed time Alpha- adrenergic antagonists: b. Phentolamine:  blocks alpha1 and alpha2 receptors  treatment of pheochromocytoma  prevention of tissue necrosis following extravasation of drugs that produce alpha1-mediated vasoconstriction Alpha- adrenergic antagonists: b. Phentolamine: Adverse effects:  Like prazosin  Produces greater reflex tachycardia than prazosin due to alpha2 blockade  Overdose can produce profound hypotension  elevate BP with NE. Epinephrine should not be used? Beta- adrenergic antagonists: Therapeutic applications:  Angina pectoris: by blocking beta1 receptors in the heart decrease cardiac work  Hypertension: Beta adrenergic blocking agents are drugs of choice for hypertension  Cardiac dysrhythmias: Blocking cardiac beta1 receptors  decrease the rate of sinus nodal discharge and suppress conduction of atrial impulses through the AV node Beta- adrenergic antagonists: Therapeutic applications:  Myocardial infarction: MI: region of myocardial necrosis caused by localized interruption of blood flow to the heart wall  Migraine: If taken prophylactically they can reduce the frequency of migraine attack Beta- adrenergic antagonists: Adverse effects:  bradycardia  reduced cardiac output: - by decreasing heart rate and force of contraction - beta blockers must be used with great caution in patients with heart failure or reduced cardiac reserve Beta- adrenergic antagonists: Adverse effects:  AV heart block:  Rebound excitation: - Increased cardiac activity in response to abrupt cessation of beta blocker therapy - Long term use of beta blockers  sensitize the heart to catecholamines - If withdrawn abruptly  anginal pain or dysrhythmias - Withdraw gradually taper the dose over a period of 1 to 2 weeks (Note:warn patients against abrupt cessation. Carry adequate supply of beta blockers when traveling( Beta- adrenergic antagonists: Adverse effects:  Bronchoconstriction: Beta2 blockers are contraindicated in asthma  Inhibition of glycogenolysis: If diabetic patient requires a beta- blocker, a beta1-selective agent should be chosen Beta- adrenergic antagonists: a. Propranolol  nonselective beta adrenergic antagonists  highly lipid soluble Therapeutic uses:  hypertension  angina pectoris  cardiac dysrhythmias  myocardial infarction  migraine headache Beta- adrenergic antagonists: a. Propranolol Adverse effects:  refer to previous adverse effects  in addition CNS effects: - depression and insomnia - nightmares and hallucinations - used with care in patients with a history of depression Beta- adrenergic antagonists: a. Propranolol Precautions and contraindications:  should be avoided in patients with a history of anaphylaxis  must be used with caution by diabetic patients: - suppress glycogenolysis - masking tachycardia - warn the patients that tachycardia is no longer an indication of hypoglycemia - should be taught alternative signs: sweating, hunger, fatigue, poor concentration) Beta- adrenergic antagonists: a. Propranolol Drug Interactions:  calcium channel blockers: cardiac effect of certain calcium channel blockers (e.g. verapamil) are identical to those of propranolol  impeded early recognition of insulin induced hypoglycemia Note: the dosage must be adjusted by monitoring the patient’s response and not by relying on dosing information in a drug reference Beta- adrenergic antagonists: b. Metoprolol:  Cardioselective agent  Preferred for patients with asthma or diabetes  Hypertension, angina pectoris, myocardial infarctions  Deprive the diabetic patient of early indication of hypoglycemia Beta- adrenergic antagonists: c. Pindolol::  partial agonist activity intrinsic sympathomimetic activity (ISA)  binding to a receptors produces limited degree of receptor activation while preventing strong agonists from binding to the receptor to cause full activation  have very little effect on resting heart rate and cardiac output  preferred for patients with bradycardia  C.I. in MI