CV II - Antihypertensive agents

Question 1

How is hypertension diagnosed?

Answer 1

High BP measured multiple times

Question 2

What is mild hypertension?

Answer 2

Over 140/90 mm Hg

• Asymptomatic until damage to heart, brain, retina, kidney etc. occurs
• systolic/diastolic

Question 3

What is primary hypertension?

Answer 3

Unknown cause of hypertension

The cause is known in 10-15% cases

Question 4

True or false? Blood pressure control mechanisms are working normally in hypertensive people

Answer 4

True

Question 5

Give the two systems for controlling blood pressure

Answer 5

SNS: Fast control.

Renin-angiotensin system (RAS): Longer term control.

Question 6

How does the CNS control blood pressure?

Answer 6

• Carotid baroreceptors senses low blood pressure and send a signal to raise blood pressure to the brain
• Sympathetic NS ganglia activated
• β1 receptors in heart increase heart rate and contraction force
• β1 receptors in kidney increase renin secretion
• α1 receptors constrict vascular smooth muscle veins

Question 7

How does the renin-angiotensin system control blood pressure? Describe pathway.

Answer 7

• Angiotensin converted to angiotensin I by renin
• Angiotensin I converted to angiotensin II by ACE (angeiotensin converting enzyme)

Angiotensin II:

• α1 receptors cause vasoconstriction on vascular smooth muscle
• Aldosterone released, causing sodium and water retention

Question 8

What four types of drugs are used to treat hypertension?

Answer 8

• Diuretics
• Drugs that affect the SNS (centrally acting, β blockers, α1 blockers)
• Vasodilators (Ca channel blockers, other)
• Drugs that affect the RAS (ACE inhibitors, AII antagonists)

Question 9

True or false? Hypertension often requires polypharmacy

Answer 9

True. Though monotherapy is always preferable.

Some effective drugs have toxic effects at maximal doses, so additional drugs with different mechanisms of action can be added

Question 10

How do diuretics treat hypertension?

Answer 10

• Act on cells in renal tubule to promote diuresis (water excretion) and naturiesis (sodium excretion)
• Depletion of Na in body decreases stiffness of vascular smooth muscle cells
• Initial decrease in BP due to decreased blood volume and reduced cardiac output
• Over time CO returns to normal but lowered peripheral resistance can be left lowered by 10-15 mm Hg (may be all you need)
• Effective and safe, especially in elderly (over 85)

Question 11

What are the three types of diuretics most commonly used to treat hypertension?

Answer 11

• Loop diuretics
• Thiazides
• Potassium sparing diuretics

Question 12

How do loop diuretics work?

Answer 12

• Ascending loop of henle
• Chlorine/sodium/potassium transporter brings sodium back into body, loop diuretics inhibit this transporter
• Sodium, potassium and water loss
• VERY POWERFUL

Question 13

How do thiazides work?

Answer 13

• Distal convoluted tubule
• Inhibits Na reuptake
• Sodium and potassium lost
• Used along with K-sparing diuretics for hypertension

Question 14

How do potassium sparing diuretics work?

Answer 14

• Collecting tubule
• Inhibit Na/K pump
• K accumulates (not excreted)
• Na and water excreted (lost)
• Used along with thiazides for hypertension

Question 15

How do centrally acting SNS drugs lower blood pressure?

Answer 15

• Decrease SNS outflow by inhibiting hypothalamic SNS activity
• Causes sedation as well, so not popular, used for eclampsia in pregnant women

Question 16

How do beta blockers decrease blood pressure? Who shouldn’t take them?

Answer 16

• β1 receptor cardioselective
• Decrease HR and reduce force of contraction (reducing CO and BP)
• Over the long term beta blockers decrease renin release

Asthmatics should not take beta blockers

Question 17

How do α1 blockers reduce blood pressure?

Answer 17

Causes vasodilation on vascular smooth muscles

• Effectively blocks effects of SNS on blood vessels

Question 18

What are some adverse effects to α1 blockers?

Answer 18

Orthostatic hypotension

• Sudden decrease in BP upon standing
• Other SNS effecting drugs can do this as well

Question 19

How do calcium channel blockers lower blood pressure? Name two.

Answer 19

They inhibit influx of calcium and therefore cause relaxation of vascular smooth muscle cells

Used to treat: angina, hypertension and arrhythmia

Nifedipine: acts on blood vessels only

Diltiazem and verapamil: Both heart and blood vessels

Question 20

Name three other vasodilators in addition to calcium channel blockers

Answer 20

• Hydralazine (pregnancy safe)
• Sodium nitroprusside (emergency drug)
• Minoxidil (Rogaine)

Question 21

Why can’t you use ACE inhibitors or angiotensin II inhibitors during pregnancy?

Answer 21

Teratogenic (fetal malformations)

Question 22

How do angiotensin II antagonists lower blood pressure?

Answer 22

Block AII receptors causing vasodilation and a decrease in BP

Block of receptors at adrenal gland causes a decrease in aldosterone release, leading to decrease in sodium and water retention and a decrease in BP.