Antihypertensives

Question 1

At what BP should treatment be started for HTN?

Answer 1

Systolic - 160

Diastolic - 100

Question 2

What are some risk factors for HTN?

Answer 2

Smoking, obesity, hyperlipidaemia, diabetes and left ventricular hypertrophy.

HTN can also be secondary to renal and endocrine disease.

Question 3

What is the initial of mild HTN?

Answer 3

Lifestyle changes

Question 4

What are the main categories of drugs used to treat HTN?

Answer 4

1) Ace inhibitors
2) Angiotensin II receptor antagonists
3) Calcium chanel blockers
4) Beta-blockers
5) Thiazide diuretics
6) Alpha -1-adrenoreceptor antagonists

Question 5

Give 2 examples of thiazide diuretics

Answer 5

Bendroflumethiazide

Indapamide

Question 6

What are the side-effects of thiazide diuretics?

Answer 6

Hypokalaemia, diabetes mellitus, gout.

At therapeutic doses these metabolic effects are rare.

Question 7

How are thiazide diuretics thought to treat HTN?

Answer 7

After the initial fall in blood pressure due to decreased blood volume, venous return and cardiac output, the cardiac output returns to normal but the peripheral resistance has decreased. This is possibly due to lower plasma Na+ levels leading in turn to lower Ca++ in smooth muscle cells.

Question 8

Which patient group are thiazide diuretics particularly useful in?

Answer 8

Older patients (>55)

Question 9

How do Beta-blockers treat HTN?

Answer 9

Not hugely sure…Initially they cause a fall in cardiac output. This returns to normal and the peripheral resistance is ‘reset’ at a lower level…Could be to do with the blockade of beta-1 receptors in the juxtaglomerular granule cells that secrete renin.

Question 10

What are the common side-effects of beta-blockers?

Answer 10

Cold hands, fatigue, provocation of asthma, heart failure and conductance block. Cause a rise in serum triglycerides and decrease HDL cholesterol levels.

Question 11

Name 3 beta-blockers

Answer 11

Non-selective (B1/2) - Propanolol

B1 selective - Atenolol, Metopralol

Question 12

How do ACE inhibitors work?

Answer 12

Prevent the formation of angiotensin II in the lung epithelium.

Question 13

What are the side-effects of ACE inhibitors?

Answer 13

Relatively few, bradykinin cough can occur.
Rare complications involve angioedema, proteinuria and neutropenia
Hyperkalaemia is not a common complication unless patient is K+ supplement or K+sparing diuretics

Question 14

What is the relationship to ACE inhibitors and kidney disease?

Answer 14

It can cause renal failure in patients with bilateral renal artery stenosis, for they rely on angiotensin II to constrict postglomerular efferent arterioles to maintain filtration.

Question 15

Give 3 examples of ACE inhibitors.

Answer 15

Captopril
Enalapril
Ramipril

Question 16

Name an angiotensin receptor blocker, how it works and why it is good.

Answer 16

Losartan, lowers blood pressure by blocking angiotensin receptors (AT1). It has the benefit of not causing a bradykinin cough.

Question 17

How do calcium channel blockers work?

Answer 17

The bind to the L-type calcium channels on vascular smooth muscle and prevent the influx of calcium, thereby causing relaxation. This reduces peripheral resistance and therefore BP.

Question 18

Give three examples of calcium channel blockers.

Answer 18

Amlodipine - Long half life 40hrs
Nifedipine - half life 2hrs
Verapamil - half life 4hrs. It has arteriolar and some venous dilatory effects. It is also negatively inotropic and chronotropic. Should not be used in patients with bradycardia, heart block, Wolf-Parkinson-White syndrome. Amiodarone and digoxin increase the AV conduction block.
Diltaizam - half life 5hrs, similar effects as verapamil but less myocardial depression and AV conduction prolongation.

Question 19

How do alpha-1-adrenoreceptors antagonists reduce HTN?

Answer 19

They selectively block vascular alpha-1-adrenoreceptors. Their selectivity prevents them from causing tachycaradias. They are used in conjunction with other hypotensives in resistant HNT

Question 20

Give two examples of alpha-1-adrenoreceptor antagonists.

Answer 20

Prazosin

Doxazosin

Question 21

Which are the centrally acting antihypertensives and what is their mechanism of action?

Answer 21

Methyldopa - converted in adrenergic nerve endings to the false transmitter alpha-methylnoradrenaline, which stimulates alpha-2 receptors in the medulla and reduces sympathetic outflow. Can cause drowsiness and in 20% of patients a positive coombes test.
Clonidine