Alpha Blockers HTN Flashcards
Activation of alpha 2 receptors cause what?
Activation of the receptor decreases production of cAMP leading to an inhibition of further release of NE from the neuron
Activation of alpha 2 receptors cause what?
increased production of DAG and IP3, leading to an increase in Ca2+
Receptors NE act on?
alpha1/2, beta1
Receptors E act on?
alpha1/2, beta1/2
Drugs with high alpha 1 affinity?
Terazosin, Doxazosin, Prazosin
Drugs with equal alpha 1 and 2 affinity?
Phenoxybenzamine and Phentoloamine
Where alpha-1b and alpha-1d receptors are?
In vasculature; involved in smooth muscle contraction
Alpha-1a receptor present where?
In bladder neck and prostate; blockade of it can improve urine flow and reduce symptoms from BPH
Alfuzosin action?
Block alpha-1a receptor; used to treat BPH
Adverse effects of Alpha Blockers?
First dose orthostatic hypotension; sinus-tach (angina, palpitations), syncope, vertigo
Which type of alpha receptors most often cause tachycardia?
Alpha-2-presynaptic receptors
Phenoxybenzamine
Non-competitive (covalent) alpha-1,2 antagonist; used for pheochromocytoma, raynaud’s, frostbite, and acrocyanosis; slow onset long duration; S.E. - sinus tach and nasal congestions (minor affect on histamine); also cause drowsiness, fatigue, malaise, confusion, headache, xerostomia, and ejaculation dysfunction
Phentolamine
Short acting competitive at alpha1/2 receptors; used for pheochromocytoma and HTN emergency;
small doses - increased BP
large doses - decreased BP
Postural hypotension is a prominent feature; reflex tachycardia is a prominent feature - limit use of drug for essential hypertension
Reason for decline in use of alpha blockers
Do not show greater benefit than ACE inhibitors and have higher risks.
Affects of beta receptors in heart
Accelerate SA node and ectopic pacemakers
Increase contractility
