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Bind to adrenergic receptors but instead of stimulating agonists we can divide antagonists based on their affinity for alpha or beta alpha blockers and beta blockers so let’s start with alpha blockers first smooth muscle receptors which results in vasodilation and thus lowering of blood now alpha blockers can be subdivided into two groups that is non-selective non-selective
Agents can block both alpha-1 are phentolamine and phenoxybenzamine which are used in the treatment of adrenal glands that secrete norepinephrine and epinephrine now we are non-selective they also block alpha-2 receptors which as you may remember now norepinephrine acts on alpha-2 receptors to inhibit its own release so norepinephrine then can stimulate beta-1 receptors
On the heart this is why non-selective drugs such as phentolamine and phenoxybenzamine can cause irreversible antagonist and the only way the body can overcome its effects is by hand phentolamine is a reversible antagonist and that’s why its effect blockers and let’s discuss alpha-1 blockers first so these agents selectively and reversibly block alpha-1 receptors located
Mainly in vascular blood pressure and they also block receptors in the smooth muscle of the leading to relief of the urinary difficulties associated with benign now examples of alpha-1 selective blockers include prazosin doxazosin terazosin tamsulosin alfuzosin and silodosin and note that this alpha-1 blocker now the first three of these that is prazosin doxazosin and on
Relieving symptoms of enlarged prostate on the other hand tamsulosin more effective for relieving symptoms associated with enlarged prostate and receptors in the prostate specifically alpha-1a subtype now when it comes to alpha-1 blocker although it’s not as severe as that produced by alpha-1 blockers can lead to headaches and nasal congestion blockers have very limited
Clinical application in humans and they’re used mainly in research one example of alpha-2 blocker that you may encounter is much beneficial evidence supporting its use in humans on the other hand yohimbine is used sometimes in veterinary medicine to reverse sedative effects beta blockers so just like alpha blockers beta blockers can also be alpha blockers beta blockers can
Also be competitive inhibitors at beta adrenergic receptors and they counter leads to decrease in sympathetic effects mainly on cardiovascular system this is heart attacks angina and cardiac arrhythmias additional uses include discussing first generation beta blockers which also happen to be example of these agents include propranolol pindolol or nadolol based on blockade of
Beta-1 receptors on the heart which results in decreased the final outcome is decreased cardiac output and decreased oxygen demand of can also penetrate into the cns and was found to be effective for migraine prophylaxis on the other hand timolol when applied topically to the for a treatment of glaucoma however all that being said let’s not forget recall beta-2 receptors
Are predominant in lungs so their blockade can actually are not recommended in patients with copd or asthma now let’s move on to the receptors and because of that we also call them cardio-selective beta blockers chronic lung disease however keep in mind that at high enough doses this beta-1 these agents include atenolol acebutolol bisoprolol esmolol and metoprolol now
Special attention because things can get a little tricky so unlike the first generation group that included non-selective agents and unlike the second includes both non-selective and selective beta blockers however what they also act on blood vessels to cause vasodilation so here we have produce peripheral vasodilation by blocking not only beta but also alpha-1 nebivolol
Which produce vasodilation by inducing the release of nitric oxide by additionally blocking calcium channels and just as a side note here applied topically to the eye just like timolol it is often prescribed for third generation beta blockers make these agents especially effective in shown to have antioxidant properties which make them beta blockers of choice i wanted to
Briefly discuss intrinsic sympathomimetic activity of couple beta blockers namely pindolol and acebutolol now these two beta blockers are a stimulate both beta-1 and beta-2 receptors which leads to diminished effect activity can actually be beneficial in patients who cannot tolerate other beta before we end you may wonder well what about beta-2 blockers and the short with
That i wanted to thank you for watching i hope you enjoyed it and as
Transcribed from video
Pharmacology – ALPHA & BETA BLOCKERS – ADRENERGIC ANTAGONISTS ( MADE EASY) By Speed Pharmacology
