5 Drugs and the Heart

Question 1

How can drugs affect the heart?

Answer 1

directly (rate/rhythm, or contraction force)

Indirectly (vasculature or blood volume (renal))

Question 2

Name 2 examples of Class I antiarrhythmic drugs

Answer 2

lidocaine

flecainide

Question 3

How do class I antiarrhythmic drugs work?

Answer 3

block Na+ VGC’s (dirty tho)

slow the rate of depolarisation, increasing the refractory period

Question 4

Name one example of a class II antiarrythmic drug

Answer 4

metoprolol (beta blocker)

Question 5

How do Class II antiarrythmic drugs work?

Answer 5

decrease sympathetic effect

Question 6

Name 2 examples of Class III antiarrythmic drugs

Answer 6

amiodarone

sotalol

Question 7

How do Class III antiarrythmic drugs work?

Answer 7

block K+ channels, lengthening repolarisaiton prolonging AP

Question 8

Name one side effect of amiodarone

Answer 8

it contains iodine so it impairs thyroid function

Question 9

How does adenosine work?

Answer 9

binds to receptors in the SA/AV, opening K+ channels

more K+ efflux

hyperpolarisation, increases refractory period, as nodal conduction slows

Question 10

How does caffeine increase HR?

Answer 10

antagonist to adenosine receptors in the SA/AV, therefore closing K+ channels, making cells more excitable

(opposite to adenosine)

Question 11

in what 2 circumstances would we need drugs to affect the force of contraction?

Answer 11

anaphylaxis

heart failure

Question 12

What are the 2 sorts of inotropic drugs?

Answer 12

+ inotropic drugs increase intracellular Ca2+

• inotropic drugs decrease intracellular Ca2+

Question 13

Name one type of cardiac Glycosides

Answer 13

digoxin

Question 14

How does digoxin increase contractility?

Answer 14

partial inhibition of Na+ / K+ ATPase

this reduces the Na gradient increasing Na intracellular concentration, reducing the amount of calcium that can be pumped out via the Na/Ca pump

Question 15

What side effects are associated with cardiac glycosides?

Answer 15

ionic disturbance (can cause arrythmia if too much, or GI symptoms)
gynaecomastia (iodine and thyroid)

Question 16

What is Digoxin used for?

Answer 16

heart failure patients with arrhythmia

Question 17

What drug interactions should we watch out for with Digoxin

Answer 17

diuretics reduce K+ levels, this promotes the digoxin effect as K+ isn’t competing with digoxin as much

Question 18

How do PDE inhibitors work?

Answer 18

increases cAMP / cGMP levels and hence allows more Ca2+ in, increasing contraction force

Question 19

Why are PDE inhibitors so useful?

Answer 19

PDEi type 3 are mainly expressed in the heart

Question 20

What is a potential adverse effect of using PDE inhibitors?

Answer 20

arrhythmia

Question 21

When are PDE inhibitors used?

Why?

Answer 21

acute heart failure - emergencies

they have a short half life

Question 22

Name 3 types of drugs used for cardiac failure which don’t have a direct effect on heart cells

Answer 22

diuretics (decrease blood volume)
vasodilators (increase systemic volume)
ACE inhibitors

Question 23

Name 2 other drugs used to decrease heart rate

Answer 23

beta blockers

ivabradine

Question 24

How does ivabradine work?

Answer 24

blocks the IF channel in cardiac myocytes, which is important in determining pacemaker potential

this decreases HR

Question 25

How does Digoxin increase HR?

Answer 25

decreases Vagal tone