Hf Drugs

Front 1

Digoxin (di-jox’-in)

Back 1

• Administration Oral or iv
• Elimination: 2/3 are eliminated by kidney
• T1/2 – increased in renal insufficiency
• Use: Heart Failute, Arrhythmia
• Actions:
o ↑ contractility
o vagal stimulation – important in treating A-fib
o ↓ sympathetic activity
• Mechanism – inhibits sarcolemma Na,K-ATPase → ↑ Na inside → ↑ Ca inside → ↑ myocardial contractility

Front 2

Effects on electrical system of heart are important in digoxins ability to treat A-fib:

Back 2

• Digoxin stimulates the vagus
• Vagus – innervates upper parts of heart –
o SA → ↓ HR
o Atria → ↓ ERP (less impulses conduction)
o AV → ↑ ERP, ↓ conduction velocity
• Some CCB can also slow conduction – so are also used for A-fib

Front 3

Describe the manifestations of digitalis toxicity, including cardiac, gastrointestinal, and CNS effects.

Back 3

i. Cardiac:
1. SNS stimulation – many types of arrhythmias
2. Delayed After depolarization (associated with ↑ [Ca] in side the cell → ↑ membrane potential
ii. GI:
1. Anorexia
2. Nausea & vomiting
3. diarrhea
iii. CNS:
1. Confusion, mental disturbances, blurred vision, or abnormal color vision

Front 4

Describe the interactions between digoxin and each of the following drugs:

Back 4

i. Diuretics (thiazide or loops) – hypokalemia
ii. Quinidine – antiarrhythmic (was used with digoxin for a-fib)
i. Quinidine inhibits p-glycoprotein, which is used to remove digoxin from the body – so you must lower the dose of digoxin
iii. Verapamil (CCB) → ↑ plasma digoxin
iv. Amiodarone (antiarrhythmic drug) → ↑ plasma digoxin
v. St. John’s Wort → ???
vi. Antacids, Chylestyramine → ↓ plasma digoxin (bind in GI tract)

Front 5

Digitalis toxicity – some aspects of treatment

Back 5

a. Potassium management – hypokalemia → ↑ digoxin binding → ↑ risk toxicity
b. Arrhythmias
c. AV block
d. Digoxin immune fab (ovine – sheep) - Used to treat digoxin toxicity

Front 6

Digoxin immune fab (ovine)

Back 6

Used to treat digoxin toxicity

Front 7

Describe the serum electrolyte disturbances that increase the risk of digoxin toxicity.

Back 7

ii. hypokalemia → ↑ digoxin binding → ↑ risk toxicity
iii. hypercalcemia → ↑ risk toxicity
iv. hypomagnesemia → ↑ risk toxicity
v. hyperkalemia → ↓ digoxin binding

Front 8

Explain the significant of age and renal function as possible risk factors for digoxin toxicity.

Back 8

Old age → ↓ Renal clearance of digoxin → ↑ risk toxicity

Front 9

Dobutamine

Back 9

β1 agonist
1. iv infusion
2. Adverse Effect:
o Excessive ↑ HR
o Arrhythmias

Front 10

Milrinone

Back 10

• cAMP PDE inhibitor → ↑ contractility, vasodilation
• Effects:
o ↓ PCWP (a measure of preload)
o ↓ PVR
o ↑ CO
• Administration: i.v., only for severe, acute heart failure
• Adverse effects:
o Arrhythmias

Front 11

Nesiritide (ni-SIR-i-tide)

Back 11

• Recombinant BNP
• Used for severe, acute heart failure
• Causes naturesis and vasodilation
• Effects:
1. ↓ PCWP (a measure of preload) → ↓ dyspnea
• Administration: iv
• Adverse Effects:
i. Hypotension
ii. Reports of renal damage and deaths