Chapter 24

Pharmacology: An Introduction - Chapter 24: Antianginal Drugs

Learning Outcomes

  • 24.1 Types and Causes of Angina Pectoris

    • Describe the main types of angina pectoris and the usual cause of each type.

  • 24.2 Nitroglycerin Mechanism of Action

    • Discuss the mechanism of action of the nitrate drugs and compare routes of administration and onset of action of the different nitrate preparations.

  • 24.3 Beta-Blockers in Angina Treatment

    • Explain the mechanism of action of beta-blockers in the treatment of angina and coronary artery disease (CAD).

  • 24.4 Pharmacologic Effects of Calcium Channel Blockers

    • Recognize the pharmacologic effects produced by the different calcium channel blockers.

  • 24.5 Preferred Therapies for Angina

    • Discuss the preferred therapies for the different types of angina.

Nitrates

  • General Effects

    • Produce a general vasodilation of systemic veins and arteries.

    • Administered:

    • During angina attacks to relieve pain.

    • On a daily basis to prevent angina attacks.

  • Mechanism of Action

    • Nitric oxide relaxes vascular smooth muscle.

    • Vasodilation decreases both preload and afterload on the heart.

  • Clinical Use:

    • Sublingual Nitroglycerin:

    • Relieves acute angina attacks.

    • Nitroglycerin Ointment (2%):

    • Helps prevent the occurrence of angina.

    • Nitroglycerin Extended-Release Capsules:

    • Used daily as a form of prophylaxis.

    • Transdermal Nitroglycerin (Nitro-Dur, Minitran):

    • Used in the prevention of angina.

    • Intravenous Infusion of Nitroglycerin:

    • Used during emergency and surgical situations.

  • Adverse Effects:

    • Cutaneous flushing

    • Dizziness

    • Headache

    • Weakness

    • Fainting

    • Sudden drops in blood pressure can cause reflex tachycardia.

  • Patient Education:

    • Patients must carry the prescribed medication at all times.

    • Tablets must be stored in light-resistant, airtight containers.

    • Individuals experiencing angina should sit down and place a nitroglycerin tablet under the tongue.

    • Awareness of side effects is critical for effective management.

  • Drug Interactions:

    • Nitrate drugs should not be combined with drugs treating erectile dysfunction.

    • This combination can cause excessive vasodilation, hypotension, reflex tachycardia, and potentially lead to myocardial infarction.

Calcium Channel Blockers

  • Mechanism of Action:

    • Inhibit the influx of calcium ions into vascular smooth muscle.

    • Enable arteriolar vasodilation and reduce blood pressure.

    • These are administered daily to prevent angina and are preferred for treating variant or Prinzmetal angina, and to relieve vasospasm.

  • Drugs with Direct Cardiac Effects:

    • Verapamil:

    • Used to treat supraventricular arrhythmias and angina.

    • Diltiazem:

    • Possesses greater vasodilating effects compared to verapamil.

  • Adverse Effects:

    • Headache

    • Facial flushing

    • Dizziness

    • Hypotension

    • Minor gastrointestinal disturbances

    • Overdose Symptoms for Verapamil and Diltiazem:

    • Bradycardia

    • Atrioventricular (AV) block

    • Decreased myocardial contraction

    • Possible heart failure

    • Contraindications:

    • The use of calcium channel blockers is contraindicated with beta-blockers due to risk of excessive cardiac depression and heart failure.

Ranolazine (Ranexa)

  • Overview:

    • Ranolazine is a piperazine antianginal agent.

    • It exerts antianginal and anti-ischemic effects without altering heart rate or blood pressure.

    • Indicated for chronic angina pectoris as a maintenance medication.

  • Adverse Effects:

    • Dizziness

    • Constipation

    • Headache

    • Nausea

    • QTc prolongation

Preferred Therapy for Angina Pectoris

  • Exertional, Fixed, or Stable Angina:

    • Preferred treatments include nitrates, beta-blockers, and calcium channel blockers.

  • Variant or Prinzmetal Angina:

    • Preferred treatments include calcium channel blockers and nitrates.

  • Unstable Angina:

    • Managed with antiplatelet and anticoagulant therapy, along with lifestyle changes to provide better patient outcomes.