Cardiovascular Pharmacology

Question 1

Cardiac glycosides (+myocardial contractility)

Answer 1

Digoxin
Digitoxin
Ouabain

Source Foxglove (digitalis spp)

Question 2

Cardiac glycosides actions

Answer 2

Cardiac slowing and reduce rate of conduction through AV node
Increase force of contraction. Myocardial contractility

+Inotropic: squeeze/contract harder

• chronotropic: beats slower
• dromotropic: slows impulses sent through AV node

Outcome: hrt squeezes more blood out = increased stroke volume = increased CO

Question 3

MoA of cardiac glycosides

Answer 3

Inhibit Na, K ATPase enzyme (selectively binds ion transport ax cell membranes by binding on enzyme)
Increase activity of vagus nerve

Question 4

Digoxin treats

Answer 4

Heart failure
Cardiogenic shock
Atrial Fibrillation/flutter

Ie issues with heart pumping and emptying

Question 5

Causes of digitoxin toxicity

Answer 5

Electrolyte imbalances
Hypokalemia(k)
Hypomagnesemia
Hypercalcemia

Pts most vulnerable to digitoxin toxicity
The elderly. Have compromised renal and liver fxn.

Question 6

Adverse effects of cardiac glycosides

Answer 6

Reduced AV conduction
Increased ectopic pacemaker activity
Nausea, vomiting, diarrhea
Confusion

Question 7

Ouabain pharmacokinetics

Answer 7

Low lipid solubility
Poor oral BA
Half life - 21hours
Not bound to plasma protein
Not metabolized
Vd 18L/kg

Question 8

Digoxin pharmacokinetics

Answer 8

Medium lipid solubility
Bioavailability of 75%
Half life 40hrs
PPB of 20-40%
Less than 40% is metabolized
Vd 6L/kg

Question 9

Digitoxin pharmacokinetics

Answer 9

High lipid solubility
More than 90% BA
Half life 168 hrs
More than 90% PPB
Largely metabolized
Vd 0.6L/kg

Question 10

Metabolism and excretion of cardiac glycosides

Answer 10

2/3rds of digoxin excreted unchanged thru renal system (renal clearance proportional to creatinine clearance)
Digitoxin metabolized in liver and excreted thru hepato billiary route.
Ouabain parenteral admin n lost unchanged

Question 11

Cardiac effects of digoxin

Answer 11

+ cardiac contractility
Electrical effects on heart circulation
Autonomic effects: lower doses are parasympathetic with atropine-like blockade esp in elderly pts.
Toxic levels +se sympathetic outflow

Question 12

How digoxin affects other organs

Answer 12

Smooth muscle: excite
CNS: Excite, disorientation, hallucinations, aberration of color perception, convulsions
GIT: Anorexia, Nausea, Vomiting, diarrhea
Gynecomastia