Antihypertensive Drugs

Question 1

What are the three broad drug strategies to reduce hypertension?

Answer 1

1. Reduce cardiac output
2. Dilate resistance vessels
3. Reduce blood voume

Question 2

How does the renin-angiotensin system work?

Answer 2

SNS or reduced renal blood flow (juxtaglomerular apparatus) triggers release of renin.

Renin converts angiotensin precursor to angiotensin 1.
Angiotensin converting enzyme (ACE) converts angiotensin 1 to angiotensin 2.

Angiotensin 2 acts on AT-1 receptors to vasoconstrict.

AT-1 receptors on adrenal cortex respond too, reabsorbing sodium, water follows and blood volume increases

Question 3

How can the renin-angiotensin system be targeted to reduce hypertension?

Answer 3

ACE inhibitors - block the conversion of angiotensin 1 to angiotensin 2.
EXAMPLES: End in -pril

Angiotensin receptor blockers (ARBs) - Block AT-1 receptors.
EXAMPLES: End in -sartan

Question 4

How do beta blockers decrease hypertension?

Answer 4

B1-adrenoceptor antagonists (e.g. metoprolol, atenolol) causes decreased heart rate and decreased contractility. Blocking this reduces cardiac output, lowering blood pressure.

Question 5

How does Prazosin help hypertension?

Answer 5

A1-ADRs cause arteriolar vasoconstriction, increasing peripheral resistance.

Antagonising A1-ADRs (Prazosin) reduces vascular resistance and decreases hypertension.

Question 6

What are the two ways in which calcium channel blockers help hypertension?

Answer 6

Cardioselective blockers: Reduce contractility, automaticity.
EXAMPLE: Verapamil

Vascular smooth muscle selective: Reduce vascular resistance.
EXAMPLE: End in -dipine, e.g. amlodipine.