Antihypertensives & Antianginals Flashcards
Describe the mechanism of action of minoxidil.
Its metabolite activates the ATP-modulated K+ channel in arteriole smooth muscle causing hyperpolarization and relaxation. Little effect on venous and capacitance vessels.
Describe the mechanism of action of sodium nitroprusside.
It is metabolized by smooth muscle cells into the active metabolite NO. NO activates guanylate cyclase which forms cyclic GMP that then stimulates cyclic GMP-dependent protein kinase which dephosphorylates myosin light chain, reducing the contractile state of smooth muscle and causing vasodilation in arterioles and PARTICULARLY VENULES***.
What is the overall effect of sodium nitroprusside?
It reduces myocardial O2 demand and reduces preload d/t venous dilation
Describe the mechanism of action of prazosin.
It is an a1-blocker that reduces arterial resistance and venous capacitance by inhibiting vasoconstriction induced by endogenous catecholamines.
Describe the mechanism of action of guanethidine.
It is an adrenergic inhibitor that inhibits peripheral postganglionic adrenergic neurons by concentrating in neurosecretory vesicles replacing and depleting NE and blocking excitation-secretion coupling in the peripheral neurons.
*Guan takes over vesicles and gets rid of all exciting things because he’s a giant goon.
Describe the mechanism of action of hydralazine.
It is a vasodilator that causes direct relaxation on arterial vascular smooth muscle with minimal effect on venous and capacitance vessels
Which antihypertensive medications cause reflex tachycardia?
hydralazine, minoxidil, and amiloride
What are the clinical indications for sodium nitroprusside?
Primarily used for hypertensive emergencies and acute MI. It can only be given IV b/c of light sensitivity so it makes sense that it’s reserved for emergencies
What are the contraindications for hydralazine?
Patients w/ CAD and people over 40.
What are the contraindications for minoxidil?
Patients w/ CAD and ventricular hypertrophy.
*Minus oxes (they’re big like hypertrophied ventricles)
Which antihypertensive causes hair growth and is commercially sold in topical form as Rogaine?
Minoxidil
What are the side effects of prazosin and when is it used?
It frequently causes “first dose phenomenon”- orthostatic hypotension, and can also cause Na+ and water retention. It is used as an adjunct since it isn’t usually effective as a solitary tx.
What are the side effects of guanethidine?
Sympathetic dysfunction (since it depletes NE). Postural hypotension, sexual dysfunction, and diarrhea.
*Guan the goon gives people PtSD.
Describe the mechanism of action of methyldopa.
Reduces sympathetic activity by depleting NE stores in neurons. It is metabolized into a-methyl NE which is substituted in NE vesicles and it acts as an a2 agonist to reduce sympathetic activity
When is methyldopa commonly used?
Often used as an antihypertensive in pregnancy.
*Babies like meth.
What are the side effects of methyldopa?
Immunological abnormalities, dizziness, reduced libido, sedation and depression. Sudden d/c can cause rise in BP above pre-tx level.
*Babies love meth and have bad immune systems. Because they’re dopey babies.
Describe the mechanism of action of clonidine.
It is an a2 agonist that reduces sympathetic activity (just like methyldopa).
*Clonidine likes to clobber sympathetic activity to demonstrate its alpha powers.
What are the side effects of clonidine?
The same as methyldopa (except it does not cause immunological abnormalities). Dizziness, reduced libido, sedation, and depression. Sudden d/c can cause rise of BP above pre-tx levels.
What is the mechanism of action of propanolol?
It is a beta blocker, reducing contractility and CO by blocking endogenous B1 stimulation of the SA node and ventricular muscle. Also reduces renin secretion –> reduced angiotensin II levels.
What is propanolol usually used for?
Treatment for angina, arrhythmias, and may decrease mortality s/p MI. Also a good combination with nitrates!
Describe the mechanism of action of reserpine.
It is an adrenergic inhibitor (like guanethidine) that binds to storage vesicles and interferes w/ transmitter uptake system. Nerves lose ability to store NE and DA, and depletes NE in vesicles over time.
What is the overall effect of guanethidine and reserpine, both adrenergic inhibitors?
They cause a decrease in TPR via relaxation of resistance vessels and decreased sympathetic activity/vasoconstriction.
Describe the mechanism of action of amlodipine?
It is a Ca++ channel blocker that decreases contractility.
*Amlodipine doesn’t let you load up on Ca++
What are the clinical indications for amlodipine?
It treats angina and arrhythmias, and are also effective as a monotherapy for htn in low-renin populations (African-Americans, the elderly).
