Ionotropic Drugs: Limitations in Heart Failure

Question 1

What does digoxin do?

Answer 1

decrease chronotropy/ increase ionotropy (weak)

1. ^ baroreceptor activity > blocks NE > shuts off sympathetic system&raquo_space; decreased HR
2. Blocks Na/ K ATPase > increase intracellular Na > less Ca exchanged out of cell&raquo_space; more Ca

Question 2

How is digoxin excreted?

Answer 2

Renally

• careful with patients with renal dysfxn
• long half life - 7 days to steady state!
• metabolism = P-glycoprotein

Question 3

It’s important to monitor digoxin, what serum levels are desired (and don’t kill patient)?

Answer 3

.5 - 1 ng/ml

Question 4

Who would you give digoxin to?

Answer 4

• Patients with HFrEF, who aren’t responding well to treatment with ACEI/ ARBs, Beta blockers, diuretics
• All patients with sever HF symptoms
• No benefit in HFpEF!

Question 5

When do you check digoxin serum levels?

Answer 5

7 - 14 days after starting therapy

Question 6

What are the toxicities with digoxin?

Answer 6

• Heart block, bradycardia, arrythmia
• GI upset
• seeing blue/ green halos
• hyperkalemia
• confusion

Question 7

How does taking antiarrythmics affect your digoxin dosing?

Answer 7

They inhibit P-gp

-you should reduce digoxin dose by 50%

Question 8

What other medications can adversely affect digoxin levels?

Answer 8

• Azole antifungals
• Calcium channel blockers (verapamil)
• Macrolides
• quinine

*inhibitors of P-gp
Induces: rifampin, St. John’s Wort

Question 9

What effects do potassium, calcium, and magnesium have on digitoxin toxicity?

Answer 9

Toxicity from:

• hypercalcemia
• hypokalemia
• hypomagnesemia

Question 10

What medication can you give in the ER to someone who has digoxin toxicity?

Answer 10

Digoxin immune fab (ovine)

Question 11

What happens if you stop digoxin treatment instantly?

Answer 11

Exercise intolerance

Question 12

T/F: Digoxin reduces mortality

Answer 12

False- only reduces hospitalization

Question 13

Name the two big inotrope medications

Answer 13

Dobutamine

Milrinone

Question 14

What patients generally get inotropic medicine?

Answer 14

Class III - “cold and dry” (hypoperfusion)

Class IV - “cold and wet” (hypoperfusion and congestion)

Question 15

Contrast the biochemical mechanism of action of milrinone and dobutamine?

Answer 15

Milrinone: inhibits PDE > accumulation of Ca
Dobutamine: B1 agonist to stimulate G proteins > increase Ca

Question 16

With each of the following, does milrinone or dobutamine have a stronger effect?

1) vasodilation
2) enhanced inotropy
3) increased heart rate
4) tacchyarrythmia

Answer 16

Dobutamine:
enhanced inotropy
increased HR
tacchyarrythmia

milrinone:
vasodilation

Question 17

Are inotropes for short-term or long-term use?

Answer 17

Short term

Question 18

Which inotrope has a shorter half life?

Answer 18

=Dobutamine: 2 minutes
-more rapid onset/ clearing

Milrinone: 1- 3 hours
-cleared by kidneys

Question 19

If you have a hypotensive patient, which inotrope would be better?

Answer 19

Dobutamine

*milrinone has more moderate vasodilation

Question 20

If your patient is taking beta blockers, which inotrope would you use?

Answer 20

Milrinone

*dobutamine is a beta agonist

Question 21

According to the Heart Failure Society of America, when should you consider giving inotropes?

Answer 21

• Patients with advanced HF and low output syndrome
• patients have marginal BP ( to relieve symptoms and improve end-organ function
• *NOT LONG TERM
• *MAKES THEM FEEL BETTER, BUT NO BETTER OUTCOMES

Question 22

Side effects of both?

Answer 22

Milrinone: HYPOTENSION, thrombocytopenia, tachycardia, arrythmia

Dobutamine: Angina, tachyarrythmia

Question 23

Alright Dopamine is also an inotrope, but we didn’t talk about it much. How does it work?

Answer 23

Norepinephrine precursor > stimulates adrenergic receptors

Question 24

Dopamine has dose dependent effects. Explain the effects at low, moderate, and high doses?

Answer 24

RIP:
Renal - low dose > dopaminergic
Inotrope - moderate dose > beta receptors
Pressor - high dose > alpha receptor