Comprehensive Guide to Nitrates in Cardiovascular Medicine

  • Definition: Nitrates are a type of medicine that help widen blood vessels by donating a substance called nitric oxide.

  • Primary Application: They are mainly used to treat chest pain and other heart problems.

  • Authorship: Compiled by Peter M. Lee and Valerie Gerriets; updated July 10, 2023.

  • Historical Context: Nitrates were first found in 1847 to help with chest pain.

Indications and Therapeutic Use

  • General Indications: - Chest pain (both regular and sudden).

    • Sudden heart problems.

    • High blood pressure.

    • Heart failure.

  • Multifaceted Purpose: - Prophylaxis: Long-lasting nitrates help patients with stable chest pain to exercise better, especially those with heart artery disease who have other health issues.

    • Symptom Relief: Quick-acting nitrates are used for fast relief of sudden chest pain.

  • Key Nitrate Types and Specific Indications: - Nitroglycerin: Used for chest pain (both treatment and prevention), sudden heart issues, heart failure, and high blood pressure.

    • Isosorbide mononitrate: For chronic chest pain treatment.

    • Isosorbide dinitrate: For treatment and prevention of chest pain.

    • Pentaerythrityl tetranitrate: Not commonly used in the United States.

    • Erythrityl tetranitrate: Not commonly used in the United States.

Mechanism of Action

  • Activation Pathway: - Nitrates get activated in the body to produce nitric oxide, which helps relax blood vessels.

  • Molecular Cascade: 1. Nitrates change to nitric oxide.

    1. Nitric oxide activates an enzyme that raises levels of a molecule called cGMP.

    2. cGMP activates specific proteins that help relax the muscles around blood vessels.

    3. The result is a relaxed state of blood vessels.

  • Physiological Effects: - The nitric oxide pathway causes blood vessel relaxation, helps keep blood cells from sticking together, and prevents clots.

    • Venodilation: Nitrates mainly widen veins, leading to less blood returning to the heart and lowering work for the heart.

    • Cardiac Workload: Reducing how much blood comes back to the heart makes it work less hard and needs less oxygen.

    • High-Dose Effects: At higher doses, nitrates widen heart arteries more, improving blood flow during blockages or spasms.