Vasodilators

Question 1

Therapeutic uses of vasodilators

Answer 1

Main indications:
Essential Hypertension
Hypertension crisis
Angina pectoris
Heart Failure
Myocardial infarction

Other Indications
Pulmonary arterial pressure
Production of controlled hypotension during surgery

Question 1

Drugs that dilate resistance vessels (arterioles)

Answer 1

decrease cardiac work while increasing cardiac output and tissue perfusion

Question 2

drugs that dilate capacitance vessels (veins

Answer 2

• reduce cardiac preload (reduces ventricle filling)
  = decrease ventricular contraction

decrease cardiac work, output, and tissue perfusion

Question 3

effects of dilated arterioles and veins on afterload/preload

Answer 3

Dilated arterioles
-DECREASES afterload
= decreases cardiac work while increasing CO and TP

Dilate veins
-DECREASES preload
= decreased cardiac filling
= decreased vent contraction
= decreased CO and TP

Question 4

Preload

Answer 4

volume of blood in ventricles at end of diastole
- end diastolic pressure

increased in
-hypervolemia
-regurgitation of cardiac valves
-heart failure

Question 5

Afterload

Answer 5

Resistance left ventricle must overcome to circulate blood

Increased in
-hypertension
- vasoconstriction

increased afterload = increased cardiac workload

Question 6

Vasodilation Adverse Effects

Answer 6

Postural (orthostatic) hypotension
- from vasodilation of veins

REFLEX TACHYCARDIA:

-vasodilation
= reduced BP
= baroreceptors (aortic arch and carotid sinus) sense BP reduction

• baroreceptors relay info to vasomotor center in medulla
• medulla wants to bring BP up
  –> increases SNS
  = increases HR
  = reflex tachycardia
  = BP increases to pre-vasodilation level

-UNDESIRABLE- vasodilator was given to reduce BP. we want it to stay down.

Question 7

Vasodilatory drug names

Answer 7

Hydralazine

Sodium Nitroprusside

Minoxidil

Question 8

Mechanism of Action of Hydralazine

Answer 8

Blocks release of Ca from arteriole sarcoplasmic reticulum

Question 9

Cardiovascular effects of hydralazine

Answer 9

Dilation of arterioles
- decreased peripheral resistance and arterial BP

HR and hear contractility increase (reflex tachycardia)

Postural hypotension is minimal
- because action is on arterioles

Question 10

Pharmacokinetics of Hydralazine

Answer 10

PO - readily absorbed. effect in 45 min last 6 hours

Parenteral (injection/infusion)- effect in 10 min lasts 2 hours

Question 11

Therapeutic Uses of Hydralazine

Answer 11

Essential hypertension- often includes beta blocker

Hypertensive Crisis- lower BP rapidly if severe

Heart Failure- used in combo with isosorbide dinitrate to reduce afterload in heart failure

Question 12

Drug interactions Hydralazine what to combine with it

Answer 12

combine with beta blocker to prevent reflex tachycardia

diuretic to prevent sodium and water reabsorption AND RESULTING INCREASE IN BV.

Question 13

Sodium Nitroprusside (SN)

Answer 13

Drug of Choice for hypertensive emergencies

Question 14

Sodium Nitroprusside (SN) mechanism

Answer 14

SN breaks down to release nitric oxide = vasodilation

Question 15

cardiovascular effects of SN

Answer 15

venous dilation and arteriolar dilation

IV = effects begin at once
- adjusting infusion rate, BP can be decreased to desire level
-infusion stops, BP returns to previous level in minutes

Question 16

SN metabolism

Answer 16

nitric oxide to cyanide groups to thiocyanate then eliminated by liver over several days

Question 17

Therapeutic Uses SN

Answer 17

lower BP RAPIDLY in hypertensive emergencies

Question 18

Adverse Effects SN

Answer 18

excessive hypotension
cyanide poisoning
thiocyanate toxicity

Question 19

Minoxidil

Answer 19

Intense vasodilation and severe adverse reactions

reserved for patients with SEVERE hypertension unresponsive ot safer drugs

Question 20

Mechanism of Action of minoxidil

Answer 20

direct action of VSM arterioles

metabolized to metabolite that causes potassium channels to open = K+ efflux = cellular hyperpolarization
= VSM arterioles ability to contract

Question 21

Cardiovasuclar Effects of Minoxidil

Answer 21

Causes arteriolar dilation

IV = effects begin at once
- adjust infusion rate to decrease BP to desired level
- infusion stops blood pressure returns to prev. level

Question 22

Minoxidil Adverse Effects

Answer 22

Reflex Tachycardia

Serious sodium and fluid retention
- can cause cardiac compensation
- use Loop Diuretic Furosemide in combination

Hypertrichosis
- 80% of patients
- causes: proliferation of epithelial cells at base of hair follicle