Lesson 12.5. Class IV Anti-Arrythmitic Drugs

Ca-channel blockers

Class IV drugs are a.__________________ specifically b._______________.

a = ?

Nondihydropyridine

Class IV drugs are a.__________________ specifically b._______________.

b = ?

Class IV Drugs

• “state- or use-dependent” selective depression of calcium current

• AV node conduction (AV node arrhythmia) is decreased while PR interval is increased (seen in ECG)

Verapamil

prototype of Class IV drugs

activated and inactivated L-type Ca +2

CLASS IV DRUGS

Verapamil — Cardiac Effect

1. Blocks both ______________________________ -channel

2. Slows the _____ by direct action but the hypotensive effect may have small reflex increase in SA rate

3. It can suppress both ___________________________________________ and abolish response in severely depolarized tissue

1 = ?

SA node

CLASS IV DRUGS

Verapamil — Cardiac Effect

1. Blocks both ______________________________ -channel

2. Slows the _____ by direct action but the hypotensive effect may have small reflex increase in SA rate

3. It can suppress both ___________________________________________ and abolish response in severely depolarized tissue

2 = ?

EADs (early afterdepolarizations) and DADs (delayed afterdepolarizations)

CLASS IV DRUGS

Verapamil — Cardiac Effect

1. Blocks both ______________________________ -channel

2. Slows the _____ by direct action but the hypotensive effect may have small reflex increase in SA rate

3. It can suppress both ___________________________________________ and abolish response in severely depolarized tissue

3 = ?

Constipation, Lassitude, Nervousness, and Peripheral edema

CLASS IV DRUGS

Verapamil — Extra-Cardiac Effect

• ADRs include:

Hypotension and ventricular fibrillation

CLASS IV DRUGS

Verapamil — Toxicity

1. ____________________________ in patients with ventricular tachycardia

2. It can induce _____ in large doses or in patients with AV nodal disease

1 = ?

AV block

CLASS IV DRUGS

Verapamil — Toxicity

1. ____________________________ in patients with ventricular tachycardia

2. It can induce _____ in large doses or in patients with AV nodal disease

2 = ?

4-7 hrs

CLASS IV DRUGS

Verapamil — PK and Dosage

1. T1/2 is __________

2. Low bioavailability at _________ after oral administration

3. Extensively metabolized by the _____

1 = ?

20%

CLASS IV DRUGS

Verapamil — PK and Dosage

1. T1/2 is __________

2. Low bioavailability at _________ after oral administration

3. Extensively metabolized by the _____

2 = ?

liver

CLASS IV DRUGS

Verapamil — PK and Dosage

1. T1/2 is __________

2. Low bioavailability at _________ after oral administration

3. Extensively metabolized by the _____

3 = ?

supraventricular tachycardia

CLASS IV DRUGS

Verapamil — Therapeutic Use

1. It is used to terminate ______________________ (1st-line is Adenosine)

2. It can reduce ventricular rate in _________________ (rate control)

3. Occasionally, it is used for ________________________

1 = ?

atrial fibrillation and flutter

CLASS IV DRUGS

Verapamil — Therapeutic Use

1. It is used to terminate ______________________ (1st-line is Adenosine)

2. It can reduce ventricular rate in _________________ (rate control)

3. Occasionally, it is used for ________________________

2 = ?

ventricular arrhythmias

CLASS IV DRUGS

Verapamil — Therapeutic Use

1. It is used to terminate ______________________ (1st-line is Adenosine)

2. It can reduce ventricular rate in _________________ (rate control)

3. Occasionally, it is used for ________________________

3 = ?

Diltiazem

Class IV Drugs

• Similar to Verapamil in terms of clinical use

hypotension and bradyarrhythmias

Class IV Drugs

• IV Diltiazem causes less _____________________________________