Adrenergic Antagonists: Uses & Effects

mechnism of action antagonise both a1 and a2 receptor pheochromocytoma Therapeutic Use phentolamine hypertensi on cri si s due to abrupt wi thdrawal of cloni di ne postural hypotension upregulation of NE receptors Arrythmias nasal congestion toxicity headache in O2 >>myocardial ischemia Tachy cardia inNE Tolazine stimulate Histamine Hcl by acting on H2 receptor used in pulmonary hypertension in newborn infants with Respiratory Distress Syndrome differences which cause peptic ulcer Prinzmetal Angina it has high affinity to a1 receptor >>so produce less tachy cardia than phentolamine and phenoxybenzamine it crosses the nerve ,concentrate in the vesicles and replace NE,then NE is destructed by MAO enzyme >>so it inhibits its release 1-2 weeks s days and persists after stop of the therapy not used nowadays for treatment of hypertention due to its side effects and only used for refractory hypertension so No central effects like reserpine(nightmares,mental depression or sedation) mild to moderate hypertension mechanism of action Reversible onset Congestive heart failure(as it shows relative absence of tachycardia) pharmacokinetics duration(half life) Prazosine therapeutic uses BPH>>Benign Prostatic Hyperblasia>>as it antagonise a1 receptor in sphicter of urianary bladder don’t cross the CNS(not lipid soluble) Guanithidine prinzmetal Angina therapeutic uses in the initial dose(first dose phenonmenon) postural hypotenstion diarrhea toxicity destroy storage vesicle and blocks ability of this vesicle to take up and store NE and Dpamine long duration of action 18h>>one dosw per day os enough Extrapyremidal effect as parkinson’s disease >>>due to decrease in Dopamine Reserbine postural hypotension and tachy cardia Adrenergic Antagonists Toxicity toxicity receptor antagonist Irreversible PhenoxyBenzamine Labetalol B Blockers may be life threatining in patients with AV Block (partial or complete) Blocks B1 Brady cardia so withdrawal must be gradual over several weeks Sudden Withdrawal effects Mechanism of action Angina bronchospasm in patients with bronchial asthma not normal patients bronchus augments hypoglycemic effect of insulin and oral hypoglycemic hypo glycemia in diabetes as it mask signs of hypoglycemia toxicity Blocks B2 rash and fever Drug Allergy therapeutic uses used in cardiac arrhythmais like cardiac work heart rate with anti arrythmic action atrail fibrillation ischemic heart diseases prolong survival of myocardial infarction patient by slowing heart rate Obstructive hypertrophic cardiomyopathy Heart systolic pressure dissecting aortic aneurysm myocardial contraction metoprolol chronic heart failure carvidolol primary hypertension only given with a blockers pheo chromocytoma Hypertension if given alone it exaggerate the effect of catecholamines diminish portal vein pressure in patients withb cirrhosis portal hypertension as sympathetic activity may enhance the skeletal muscle tremor mechanism is UNKNOUN Essential tremors migrane and headache low dose of Propranolol CNS Anxiety Blocks B receptors Propranolol is used in anxiety and hyper throdism in part inhibits peripheral conversion of thyroxine to triiodothyronine(active form of thyroid hormone) Propranolol up regulation of B receptors and increase its sensitivity not used in prinzmetal angina not used alone in pheochromocytoma vascular supply for Extremities >>peripheral vascular disease(Cold extremities) supra ventricular arrhythmais No peripheral vascular disease thyroid hormone increase expression of B receptors IOP >>by blockin B2 receptor in the ciliary Body of the eye Hyper thyrodism Glaucoma safer to use in patients with bronchial asthma arrhythmais vascular supply for Extremities >>peripheral vascular disease(Cold extremities) CNS effects vascular supply for active musles>>due to V.C myocardial O2 demand Blocks B2 not used in bronchial athsma contradications NE effect on ANS causes sedation supraventricular tachy cardia no hypoglycemia (B2 is important in liver recovery from hypo glycemia) vascular supply for active musles>>due to V.C prolonged antagonism mental depression sleep disturbance Carvedilol AV Conduction tachy cardia&arrythmais antagonise both a1 and a2 receptor essential hypertension of pheochromocytoma used in essential hypertension(pheochromocytoma),and in hypertension during prenancy so used in chronic heart failure so we use prazosine as a blocker used in treatment of hypertension no block of B2 so heart rate(Brady Cardia) mechnism of action inhibit Oxygen free raducals Mixed a and B blockers Selective B1 Blocker may be life threatining in patients with AV Block (partial or complete) sedation, fatigue and headache produce less tachy cardia Generations Heart nasal congestion therapeutic use not used in peptic ulcer may cause haert failure has more bioviability less potent mild diarrhea, gastro intestinal cramps and increase in gastric Acid secretions contractility&excitability the same as prazosine but it is differnet in 3 items therapeutic uses postural hypotension heart failure >>>Exacerbate especialy in patients with compensated heart failure after rapid increase in the dose after addition of another antihypertensive drug Terazosine CNS Effect (Sedation,nightmare mental depression) First generation (Non selective B Blockers) postural hypotension mechanism of action hypertension Refractory Hypertension: blood pressure that remains uncontrolled in spite of maximal medical therapy (more than 5 antihypertensive drug) side effects a blocker neuron blockers compensatory sodium and water retention>>due to NE decrease lipid soluble ‫مه مين جد ا‬ peripheral vascular diseases>>raynaud’s phenomenon hypertension Refractory hypertension Classical Angina therapeutic uses Hypertension angina pectoris has withdrawl symptoms EX: metoprolol,atenolol,esmolol rd i th n o i at r e n ge But b blockers cause coroonary spasm used in chronic heart failure (with metoprolol>>second generation) increase Insulin effect inpatients with insulin resistence (prefered in diabetes) selective a1 and non selective B third generation of B blockers(non selective with aditional action)