Cardiovascular (Rate-limiting Calcium Channel Blockers)

Question 1

Examples of drugs (Rate-limiting Calcium Channel Blockers)

Answer 1

• Verapamil

- Diltiazem

Question 2

Mechanism of action (Rate-limiting Calcium Channel Blockers)

Answer 2

• Prevent cellular entry of Ca2+ by blocking L-type calcium channels.
• Myocardial and Smooth muscle contractility depressed. Cardiac contractility will be reduced.
• Dilate coronary blood vessels and reduce afterload.
• Antidysrhythmic actions due to prolonged atrioventricular node conduction – depresses heart rate.

Question 3

Indications (Rate-limiting Calcium Channel Blockers)

Answer 3

• Supraventricular arrhythmias
• Treatment of angina
• Hypertension

Question 4

Side-effects (Rate-limiting Calcium Channel Blockers)

Answer 4

- Verapamil (Constipation (up to 11.7% of patients)/Flushing/Headache/Dizziness/Hypotension (up to 2.5% of patients))
o	Diltiazem (GI disturbances (up to 6% of patients)/Bradycardia (up to 3.6% of patients)/Peripheral oedema (up to 15% of patients)/Dizziness / Headache / Hypotension (up to 4.3% of patients)

Question 5

Important pharmacokinetics/pharmacodynamics (Rate-limiting Calcium Channel Blockers)

Answer 5

• Contra-indicated in heart failure and left ventricular dysfunction due to potent negative inotropy.
• Avoid in bradycardia and hypotension.
• Do not use with beta-blockers.

Question 6

Patient information (Rate-limiting Calcium Channel Blockers)

Answer 6

• Constipation is a common side effect with Verapamil.
• Ankle swelling is a common side effect with Diltiazem, hot weather making it worse.
• Compliance is important – Patients may stop Calcium-channel blockers if they do not feel any better. Remind them that hypertension is asymptomatic but nonetheless a dangerous risk factor that needs controlled.