Class IV Flashcards
What are the three drugs in Class IV?
- Dihydropyridines (end in -pine)
- Verapamil
- Diltiazem
What is the mechanism of Class IV drugs?
- Blocks L type Ca2+ channels on VSM, cardiac myocytes and SA/AV nodes
- Vasodilation
- Decreased contractility
- Shortened phase 2 of AP
- Decreased HR
- Decreased conduction velocity in AV node
What are the cardiac effects of Dihydropyridines (end in -pine)?
- Smooth muscle selective
- Reduces systemic vascular resistance
What are the cardiac effects of Verapamil?
-Blocks activated and inactivated L type Ca2+ channels (greater effect in tissue that fire frequently, less polarized or nodal tissue)
What are the cardiac effects of Diltiazem?
-Similar to Verapamil w/ increased smooth muscle relaxation and less bradycardia
What are the extra cardiac effects of Dihyrdropyridines?
None
What are the extra cardiac effects of Verapamil?
Peripheral Vasodilation
What are the extra cardiac effects of Diltiazem?
Vasodilation
Pharmacokinetics of Dihyrdropyridines?
None
Pharmacokinetics of Verapamil?
Hepatic Metabolism (significant 1st pass)
Pharmacokinetics of Diltiazem?
Significant first pass hepatic metabolism
Toxicity of Dihydropyridines?
- Flushing, headache, excessive hypotension, edema and reflex tachycardia
- Sympathetic reflexes and lack of direct cardiac effects = poor choice for angina
Toxicity of Verapamil?
- AV block in large doses
- AV block if AV node disease
- Constipation, lassitude, nervousness, peripheral edema
- Hypotension and VFIB
Toxicity of Diltiazem?
-Hypotension and VFIB
Therapeutic use of Dihydropyridines?
-HTN
