Wk 5 Anti-Anginal Medications Review

Overview of Angina Pectoris and Myocardial Infarction

• Unstable Angina:

  • Defined as chest pain that occurs at any point in time, even during rest or sleep.

  • Represents a significant compromise in blood flow to the heart muscle compared to stable angina.

  • Requires more aggressive management than simple pain control due to the high risk of progressing to an infarction.

• Prinzmetal Angina (Variant Angina):

  • Typically occurs for a short duration, often in the middle of the night or early morning.

  • Caused by vasospasm of the coronary arteries rather than physical narrowing (atherosclerosis).

  • Sudden onset that resolves once the spasm is relieved.

• Myocardial Infarction (MI):

  • A medical emergency involving death or damage to the heart muscle due to lack of oxygen.

  • Failure to treat MI quickly can result in death, heart failure, or cardiomyopathy.

  • Clinical Manifestations:

    • Chest pain and arm pain (may radiate down the arm).

    • Diaphoresis (profuse sweating).

    • Changes in EKG readings.

    • Drop in $O_2$ saturation levels.

    • Blood pressure fluctuations (can be severely hypertensive or hypotensive).

  • Cardiac Markers:

    • Troponin: A key cardiac marker elevation indicating injury to the heart muscle.

    • High Sensitivity Troponin: A modern, more accurate standard for measuring muscle damage in hospitals.

Anti-Anginal Pharmacotherapy: Nitrates

• Mechanism of Action:

  • Induces vasodilation of the coronary arteries and peripheral vessels.

  • Benefits: Decreases myocardial workload, decreases oxygen demand, and increases oxygen supply by allowing better perfusion to the cardiac muscle.

• Common Medications:

  • Nitroglycerin (The prototype drug).

  • Isosorbide dinitrate.

  • Isosorbide mononitrate.

  • Amyl nitrate (an older variation, less commonly used today).

• Routes of Administration and Onset:

  • IV Route: Onset of $1$ to $2$ minutes; duration of $3$ to $5$ minutes. If hypotension occurs, the effect wears off quickly once the infusion is stopped.

  • Sublingual / Translingual Spray: Onset of $1$ to $3$ minutes; duration of $30$ to $60$ minutes.

  • Transmucosal Tablet: Acts similarly to the IV route in terms of rapid effect.

  • Topical Ointment: Onset of $30$ to $60$ minutes; duration of $4$ to $8$ hours.

  • Transdermal Patch: Lasts for $24$ hours (though should be removed for a "drug-free" interval).

  • Oral (Sustained Release): Effective for $8$ to $12$ hours.

• Contraindications and Drug Interactions:

  • Erectile Dysfunction (ED) Medications: (e.g., Cialis, Viagra). Use of nitrates with these medications is strictly contraindicated as it can cause extreme hypotension and potential injury.

  • Severe Anemia: Vasodilation can worsen conditions where blood volume/oxygen-carrying capacity is already low.

  • Heparin: Nitrates may decrease the therapeutic effect of heparin, requiring close monitoring of coagulation risks versus benefits.

• Adverse Effects:

  • Headache (very common due to vasodilation of cranial vessels).

  • Dizziness and Hypotension.

  • Flushing (redness of the skin due to systemic dilation).

  • Nausea and vomiting.

  • Reflex tachycardia (the heart rate increases to compensate for dropped blood pressure).

• Patient Teaching for Nitroglycerin:

  • Acute Dosing: Take one tablet sublingually every $5$ minutes for a total of $3$ doses. If pain is not relieved after the third dose, the patient must call emergency services ($911$).

  • Administration: Do not chew or swallow sublingual tablets.

  • Storage: Keep medication in its original dark glass bottle. It is sensitive to light. Store in a cool, dry place (avoid bathrooms due to moisture).

  • Transdermal Care: Remove old patches before applying new ones to avoid toxicity. Implement a "patch-off" period (usually $12$ hours at night) to prevent the development of nitrate tolerance.

Beta-Adrenergic Blockers (Beta Blockers)

• Mechanism of Action:

  • Blocks the sympathetic nervous system (SNS) response.

  • Decreases heart rate and blood pressure, thereby significantly reducing the workload of the heart.

• Common Medications:

  • Metoprolol (Prototype): Available in Oral and IV forms. IV administration results in immediate changes to blood pressure and lasts $15$ to $20$ hours.

  • Atenolol.

  • Propranolol.

  • Nadalol.

• Contraindications and Cautions:

  • Bradycardia: Do not give if the heart rate is already too slow.

  • Cardiogenic Shock: The heart is already failing; blocking the SNS can make it worse.

  • Diabetes: Beta blockers can mask the signs of hypoglycemia (specifically tachycardia and tremors).

  • Respiratory Issues: Caution in patients with COPD or bronchospasm, as even selective beta-1 blockers can sometimes affect beta-2 receptors at higher doses.

  • Thyroid Toxicosis: Can interfere with how the body responds to a thyroid storm.

• Drug Interactions:

  • Clonidine: Increases the risk of severe hypotension.

  • NSAIDs: These can decrease the antihypertensive effects of beta blockers due to the retention of sodium and water.

Calcium Channel Blockers

• Clinical Use:

  • Primary choice for Prinzmetal (Variant) Angina because they effectively decrease coronary artery spasms.

  • Less effective for typical stable or unstable angina.

• Examples:

  • Diltiazem.

  • Verapamil.

  • Nifedipine.

• Interactions:

  • Cyclosporine: CCBs can decrease the effectiveness of cyclosporine.

  • Digoxin: CCBs can increase the risk of digoxin toxicity and cause excessive drops in heart rate.

New Drug Class: Dicaraminesetamide

• Ranolazine (Ranexa):

  • The only drug in this specific new group.

  • Mechanism: Thought to act on the smaller vessels of the heart to promote vasodilation, though the exact mechanism remains unclear.

  • Benefits:

    • Decreases blood glucose levels in diabetic patients.

    • Decreases the incidence of ventricular dysrhythmias.

    • Helps with bradycardia in patients with chronic chest pain.

  • Dosing: Once-a-day extended-release tablet.

  • Contraindications: Severe hepatic impairment and lactation.

  • Adverse Effects: Headache, nausea, and constipation.

  • Key Interactions: Ketoconazole, macrolide antibiotics (erythromycin), diltiazem, verapamil, digoxin, and antipsychotics. These can significantly affect metabolism and lead to toxicity.

Lifespan Considerations

• Children:

  • Nitroglycerin is commonly used but requires precise dose adjustments based on age and weight.

• Pregnancy and Lactation:

  • Generally considered unsafe due to the risk of hypotension and fetal issues. Crosses the placenta and enters breast milk.

• Older Adults:

  • Roughly $90\%$ of older adults may be on anti-anginal medications.

  • High risk for toxicity due to slower metabolism and excretion.

  • Requires frequent monitoring of heart rate and blood pressure before administration.

Nursing Assessment

• Baseline Data: Obtain EKG, vital signs (HR, BP), and cardiac markers (Troponin).

• Pain Assessment: Use the "OLD CARTS" acronym to assess location, duration, and intensity of pain.

• Medical History: Inquire about erectile dysfunction medication use, respiratory history (COPD), pregnancy status, and history of MI.

• Physical Exam: Assess skin (especially before CCBs or nitrate patches) and respiratory effort.