Direct Acting Vasodilators Flashcards
What type of antagonist is prazosin?
Selective α₁ AR antagonist
Prazosin blocks α₁ receptors, preventing vasoconstriction and promoting vasodilation.
What is the mechanism of action of prazosin in vascular smooth muscle?
Prevents contraction by blocking α₁ receptors, leading to relaxation
Prazosin blocks the A1 receptor that usually incr intracellular Ca stores, leading to decrease in intracellular calcium and promotes dephosphorylation of actin and myosin.
What class of medication is verapamil?
Calcium channel blocker
Verapamil inhibits the calcium transporter in vascular smooth muscle cells.
What is the MoA of verapamil?
inhibits action of the calcium transporter on the transmembrane of the vascular smooth muscle cell so get ↓ overall intracellular calcium
What are potential side effects of verapamil?
Reflex tachycardia, constipation, additive effect with beta blockers
low risk 4 reflex tachy bc blockade of Ca ch->also cause cardiac suppr
Grapefruit juice can increase verapamil’s toxicity.
What is the primary use of hydralazine?
Hypertension, heart failure (esp in pregnancy)
Especially effective for hypertension and heart failure in black patients so great 1st line agent.
What is the mechanism of action of hydralazine?
Activates myosin light chain phosphatase,
Myosin LC Ptase dephosphorylates myosin, causing smooth muscle relaxation → vasodilation and decreased TPR and BP
This leads to vasodilation and decreased total peripheral resistance.
What are the side effects of hydralazine?
Reflex tachycardia, headache, fluid retention, lupus-like syndrome
Blood pressure and signs of fluid overload should be monitored.
What is the role of nitric oxide in vascular smooth muscle?
Can diffuse into vasc smooth musc cell and cause cGMP pathway.
Activates guanylyl cyclase and myosin light chain phosphatase
It leads to cGMP pathway activation and vasodilation.
How can nitric oxide lead to hyperpolarization?
Can diffuse into vasc smooth musc cell and cause cGMP pathway,
can have secondary effect of blocking calcium transporters and activating K channels (leading to hyperpolarization)
What conditions is nitric oxide used to treat?
Angina, heart failure, pulmonary hypertension
Especially effective in black patients for hypertension and heart failure.
What side effects can occur with nitric oxide?
Headache, hypotension, flushing
Careful titration is necessary to avoid excessive hypotension.
What is nitroprusside’s mechanism of action?
Stimulates NO production and activates guanylyl cyclase
This causes venous and arterial dilation, particularly coronary vasodilation.
What are the clinical uses of nitroprusside?
Hypertensive emergencies, acute heart failure
Effective in ischemic events where coronary smooth muscle requires increased oxygen.
Esp effective for HTN and HF in black patients
What side effects are associated with nitroprusside?
Hypotension, cyanide poisoning, thiocyanate toxicity
Requires close hemodynamic monitoring during use.
What type of channel does minoxidil activate?
K+ channel
Minoxidil opens ATP-sensitive K⁺ channels in vascular smooth muscle.
What is the primary indication for minoxidil?
Severe, refractory hypertension
It selectively dilates arterioles and prevents excitation-contraction coupling.
What are the side effects of minoxidil?
Reflex tachycardia, Na/H2O retention, hypertrichosis
May require concurrent β-blocker and diuretic therapy to mitigate side effects.
What is a progression side effect possibility of Minoxidil?
could cause a pericardial effusion that could progress to tamponade
What is the MoA of minoxidil?
Opens ATP-sensitive K⁺ channels in vascular smooth muscle, causing hyperpolarization and relaxation, selective dilation of arterioles
prevents excitation-contraction coupling
