Alpha blockers| Sympatholytics| Sympathoplegics- PHARMACOLOGY
This video is about sympatholytic drugs also known as adrenergic antagonists mainly alpha adrenergic blockers are discussed in this video while beta blockers will be discussed in next video sympatholytics or adrenergic antagonists are a group of drugs that bind to the adrenergic receptors and block the effects of adrenergic egginess add adrenergic receptors as
Antagonists have affinity for the receptors but no intrinsic activity as we know that there are two main types of adrenergic receptors alpha and beta receptors so there are two types of adrenergic blocking drugs drugs that block the effects of alpha receptors are known as alpha adrenergic blockers while drugs blocking the effect of beta receptors are beta blockers
Sympatholytics including the alpha and beta blockers lowers the blood pressure and heart rate and allow the blood to flow more easily through the blood vessels therefore these drugs are very useful in the treatment of cardiovascular diseases including hypertension congestive cardiac failure arrhythmias and angina these agents may cause reflex tachycardia and salt
And water retention alpha adrenergic blockers can be classified as non-selective and selective alpha blockers non-selective alpha blockers block the effect of both alpha 1 and alpha 2 receptors while selective alpha blockers block only one specific type of alpha receptors non-selective alpha blockers include phenoxy benzamine and fintolamine you can easily
Remember the names as the both words and in amine selective alpha one blockers include perezosine doxazosin terazosine cylodosine and these names can also easily remembered as these words end in osin selective alpha 2 blockers include mitaza pain which is used as an antidepressant and yohimbine which is not used clinically you just have to remember its name
For your exam so we are not going to discuss alpha 2 blockers anymore let’s discuss non-selective alpha blockers non-selective alpha blockers include phenoxy benzamine which is an irreversible non-competitive inhibitor of alpha receptors while fintolamine is a reversible competitive inhibitor at both alpha 1 and alpha 2 receptors non-selective alpha blockers are
Used to treat hypertension associated with pheochromocytoma which is a tumor of adrenal medulla in which excess of epinephrine and norepinephrine are produced now listen carefully in fiochromocytoma the treatment of choice is surgical resection of the tumor and during the operation epinephrine and norepinephrine can be released from the gland and hypertensive
Episodes can occur so phenoxy benzamine is used to prevent the hypertensive episodes during the operation as alpha 1 receptors are associated with vasoconstriction due to the blockage of alpha-1 receptors there is vasodilation and fall in blood pressure as a result postural hypotension can occur with the use of these drugs which is a major side effect of alpha
One blockers now alpha two receptors as we know that when alpha 2 receptors are activated there is decrease in sympathetic discharge conversely when there is blockage of alpha 2 receptors sympathetic discharge increases leading to increase in sympathetic tone heart rate and contractility increase is leading to tachycardia let’s talk about an important phenomena
Called vasomotor reversal of dale or epinephrine reversal it says that when non-selective alpha blockers are used before epinephrine there is a phenomena called vasomotor reversal of tail let me explain what exactly it is as we know from our previous knowledge of sympathomatics that epinephrine acts on all adrenergic receptors when epinephrine is given it acts
On alpha to alpha 1 alpha 1 receptors and due to the vasoconstriction there is initial rise in blood pressure and then there is beta 2 activation with epinephrine and vasodilation occurs so the blood pressure falls down but if alpha 1 receptors are blocked before the injection of epinephrine with alpha 1 receptor blockers then only fall in blood pressure occur
With the use of epinephrine and no initial rise in blood pressure occur this is called epinephrine reversal let me discuss the uses of fintolamine as i have discussed in sympathobatics video that the use of tyramine is contraindicated in patients taking monoamine oxidase enzyme inhibitors as there are chances of hypertensive crisis but what if hypertensive
Crises occur with the use of this combination we can use fintola main to treat such hypertensive crisis also fintola mean can be used to treat hypertensive crisis due to the abrupt withdrawal of clonidine phentolamine is also used locally to prevent dermal necrosis due to the extravasation of norepinephrine alpha one selective blockers brazosin tyrazosine and
Doxazosin are alpha one selective blockers so vasodilation occurs with the use of these agents leading to decreased total peripheral vascular resistance so these agents are used to treat hypertension while tamsolosine alfuzosin and cylodocin are also alpha 1 receptor blockers but they are more selective for alpha 1 a subtype which is found in the bladder neck
And prosthetic urethra so the use of these agents cause relaxation of the smooth muscles found in the bladder neck and prostate leading to the improved urinary flow that’s why these agents are the drug of choice for benign prostatic hyperplasia bph major adverse effect with the use of alpha one blockers is orthostatic hypotension and this effect is more pronounced
With the first dose of the drug so it is called first dose effect other adverse effects include dizziness nasal congestion headache and drowsiness all effects are due to vasodilation and one more important thing floppy iris syndrome in which there is iris which becomes flexible and it comes near the site of surgery during the intraoperative eye surgery so that’s
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Alpha blockers| Sympatholytics| Sympathoplegics- PHARMACOLOGY By SMART Medicos
