Alpha 1 receptors are located in-
Eye radial (i.e dilator) muscle
Arterioles and viens,
Male sex oegans, Urinary bladder,
Kidney and Liver.
Alpha 1 receptors use Gq Coupled secondary mediators and cause increase in phospholipase C, IP3, DAG and calcium levels in the cell.
Alpha1 blockers:
Selective Blockers- Prazosin, Doxazocin, Terazocin
Non selective Alpha blockers (both alpha 1 and alpha 2 receptor blockers)-
Phentolamine(competitive inhibitor), Phenoxybenzamine (non competitive inhibitor)
Effects of Alpha1 receptor blockage:
Eye- Miosis
Arterioles and veins- Reduced sympathetic tone in blood vessels- This results in vasodilation, Decrease in preload and after load on heart, lowering of peripheral vascular resistance and thus a fall in blood pressure is noted. The drop in blood pressure causes a reflex tachycardia.
Prazosin: Prazosin can lower BP rapidly so patients are recommended to relax for 1 hour after taking the first dose and for any increase in dose.
Ohter side effects: Orthostatic hypotension, First dose syncope, Urinary incontinence
Prazosin is used in case of lowering blood pressure in hypertensive emergencies (though I.V Sodium nitroprusside is the drug of choice in hypertensive emergencies). It decreases the tone of Urinary sphincters so it is used effectively for the treatment of BPH(Benign prostatic hypertrophy).
Eye radial (i.e dilator) muscle
Arterioles and viens,
Male sex oegans, Urinary bladder,
Kidney and Liver.
Alpha 1 receptors use Gq Coupled secondary mediators and cause increase in phospholipase C, IP3, DAG and calcium levels in the cell.
Alpha1 blockers:
Selective Blockers- Prazosin, Doxazocin, Terazocin
Non selective Alpha blockers (both alpha 1 and alpha 2 receptor blockers)-
Phentolamine(competitive inhibitor), Phenoxybenzamine (non competitive inhibitor)
Effects of Alpha1 receptor blockage:
Eye- Miosis
Arterioles and veins- Reduced sympathetic tone in blood vessels- This results in vasodilation, Decrease in preload and after load on heart, lowering of peripheral vascular resistance and thus a fall in blood pressure is noted. The drop in blood pressure causes a reflex tachycardia.
Prazosin: Prazosin can lower BP rapidly so patients are recommended to relax for 1 hour after taking the first dose and for any increase in dose.
Ohter side effects: Orthostatic hypotension, First dose syncope, Urinary incontinence
Prazosin is used in case of lowering blood pressure in hypertensive emergencies (though I.V Sodium nitroprusside is the drug of choice in hypertensive emergencies). It decreases the tone of Urinary sphincters so it is used effectively for the treatment of BPH(Benign prostatic hypertrophy).
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