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Pharmacology: Mechanisms and Compliance

Introduction to Vascular Pharmacology

  • Lecture Overview:
    • Course: HSS 3106 C - Pharmacology: Mechanisms and Compliance
    • Instructor: Professor Dr. Nehal EL-Deeb
    • Important date: March 12, 2025 - Guest speaker Samia Kadri, Pharm.D., Ph.D.

Understanding Blood Pressure (BP)

  • Blood Pressure (BP): The pressure exerted by circulating blood on the walls of blood vessels.

    • Ventricular Systole: Blood pressure rises.
    • Ventricular Diastole: Blood pressure falls.

  • Components Affecting BP:

    • Cardiac Output: Volume of blood pumped per minute, determined by heart rate and stroke volume.
    • Stroke Volume: Amount of blood pumped by ventricle per contraction.
    • Peripheral Resistance: Friction in arteries that blood encounters as it flows through.
    • Blood Volume: Total amount of blood in the vascular system.

Classification of Blood Pressure

ClassificationSystolic (mm Hg)Diastolic (mm Hg)
Normal<120 and <80
Prehypertension120-139 or 80-89
Stage I Hypertension140-159 or 90-99
Stage II Hypertension≥160 or ≥100

Types of Hypertension

  • Primary Hypertension: Unknown causes, accounts for 90% of cases.
  • Secondary Hypertension: Caused by other medical conditions such as nephrosclerosis or pheochromocytoma.
  • Hypertensive Crisis: Severe elevations in blood pressure.

Antihypertensive Medications

1. Calcium Channel Blockers

  • Functions: Slow heart rate, reduce conduction irritability, and dilate vessels.
  • Examples: Nifedipine (Procardia), Diltiazem (Cardizem), Verapamil (Calan).
    • Dosage: Range widely based on the drug and patient need.

2. Beta-Blockers

  • Mechanism: Block β1 and β2 receptors; reduce heart rate and blood pressure by causing vasodilation.
  • Commonly used for: Abnormal heart rhythms, high blood pressure, heart failure, and prevention of migraines.
  • Examples: Atenolol (Tenormin), Metoprolol (Lopressor).

3. ACE Inhibitors

  • Mechanism: Block formation of angiotensin II, which lowers blood volume and blood pressure.
  • Indicated for severe hypertension and congestive heart failure (CHF).
  • Examples: Lisinopril (Prinivil, Zestril), Ramipril (Altace).

4. Angiotensin II Receptor Blockers (ARBs)

  • Function: Block vasoconstriction effects of angiotensin II.
  • Used for hypertension and CHF management.
  • Examples: Losartan (Cozaar), Valsartan (Diovan).

5. Diuretics

  • Groups: Thiazide, loop diuretics, potassium-sparing diuretics.
    • Thiazides: First-line treatment for hypertension; enhance sodium and water excretion.
    • Loop Diuretics: More potent; used for conditions like heart failure.
    • Potassium-Sparing Diuretics: Help retain potassium while eliminating sodium and water.

6. Vasodilators

  • Mechanism: Directly relax vascular smooth muscle, causing vasodilation.
  • Examples: Hydralazine, Minoxidil.

7. Centrally Acting Adrenergic Blockers

  • Reduce vascular resistance and cardiac output via actions on the brain.
  • Common Drugs: Clonidine, Guanfacine.

8. Peripherally Acting Adrenergic Blockers

  • Function: Inhibit norepinephrine release, reducing vascular tone.
  • Examples: Doxazosin, Terazosin.

Congestive Heart Failure (CHF)

  • Definition: A condition where the heart is unable to pump sufficient blood, leading to fluid retention.
  • Treatment includes:
    • ACE Inhibitors and Beta-Blockers
    • Diuretics: Help to reduce excess fluid.
    • Cardiac Glycosides: Increase calcium levels in cardiac cells to improve contractility.

Pharmacodynamics of CHF Treatments

  • Digoxin: Increases intracellular calcium to enhance cardiac muscle contractility.
  • Beta-adrenergic agonists and Phosphodiesterase inhibitors: Improve heart performance.

Hyperlipidemia Drugs

1. Statins

  • Mechanism: Inhibit HMG-CoA reductase to lower cholesterol levels.
  • Common adverse effects: Muscle pain, liver enzyme abnormalities.

2. Bile Acid Sequestrants

  • Function: Lower LDL cholesterol by binding bile acids in the intestine.

3. Nicotinic Acid (Niacin)

  • Reduces VLDL and LDL levels; can cause flushing.

4. Fibric Acid Derivatives

  • Function: Lower triglycerides and increase HDL.
    • Note risks: Potential serious side effects, including GI disturbances.

Conclusion

  • Pharmacological treatments for vascular conditions play a crucial role in managing hypertension, CHF, and hyperlipidemia. Understanding the mechanisms behind these medications is essential for effective patient care and safety.
  • Importance of monitoring and educating patients on medication adherence and potential side effects.