Valsartan (Diovan)

Active Ingredient & Mechanism of Action

• Active Ingredient: Valsartan.
• Mechanism: Valsartan selectively blocks the binding of angiotensin II to the $\text{AT}_1$ receptor in many tissues, including vascular smooth muscle and the adrenal gland:
  1. Blood Pressure Control: By blocking the $\text{AT}_1$ receptor, it prevents angiotensin II–mediated vasoconstriction, leading to vasodilation, reduced peripheral vascular resistance, and lowered blood pressure.
  2. Reduced Fluid Retention: Blocking the receptor prevents the release of aldosterone, helping reduce sodium and water retention.
  3. Cardioprotection: By lowering total peripheral resistance and cardiac afterload, Diovan reduces stress on the heart muscle in patients with heart failure or left ventricular dysfunction following a heart attack.

Dosage Forms & Available Strengths

• Diovan 40 mg Tablets: Starting dose for heart failure or post-myocardial infarction patients.
• Diovan 80 mg Tablets: Standard starting dose for adult hypertension.
• Diovan 160 mg Tablets: Standard maintenance dose for hypertension and target titration dose for heart failure and post-MI.
• Diovan 320 mg Tablets: Maximum recommended daily dose for blood pressure control.

Clinical Indications

• Hypertension: Used as monotherapy or in combination with other antihypertensive agents (such as hydrochlorothiazide or amlodipine) to reduce blood pressure and lower the risk of stroke and heart attack.
• Heart Failure (NYHA Class II–IV): Reduces hospitalizations for heart failure in patients who are intolerant to ACE inhibitors, or as an add-on therapy when ACE inhibitors cannot be used.
• Post-Myocardial Infarction: Reduces cardiovascular mortality in clinically stable patients with left ventricular failure or left ventricular dysfunction following a heart attack.

Key Pharmacokinetics

• Absorption: Rapidly absorbed following oral administration with peak plasma concentrations ($C_{max}$) reached within 2 to 4 hours. Bioavailability is approximately 25%.
• Duration of Action: Features an elimination half-life of approximately 6 hours, but provides sustained 24-hour blood pressure reduction with once-daily dosing due to tight binding at the receptor level.
• Metabolism & Elimination: Approximately 83% is excreted in feces and 13% in urine, mostly as unchanged drug. It is not extensively metabolized by cytochrome P450 enzymes.

Administration Guidelines

• Usage: Administered orally once daily for hypertension (or twice daily for heart failure and post-MI protocols), with or without food.
• Consistency: Should be taken at approximately the same time(s) each day.
• Special Populations: Dose adjustments are generally not required for elderly patients or patients with mild-to-moderate renal or hepatic impairment.

Safety Profile & Considerations

• Common Side Effects: Dizziness, hypotension (low blood pressure), fatigue, hyperkalemia (high potassium), and increased blood urea nitrogen (BUN).
• Boxed Warning (Fetal Toxicity): Drugs acting on the renin-angiotensin system can cause injury and death to the developing fetus. Discontinue immediately if pregnancy is detected.
• Contraindications: Known hypersensitivity to valsartan and concomitant use with aliskiren in patients with diabetes.
• Key Interactions:
  • Potassium Supplements / Potassium-Sparing Diuretics: Increased risk of hyperkalemia.
  • NSAIDs: Co-administration may diminish the antihypertensive effect and increase the risk of severe renal function deterioration.
  • Lithium: May lead to increased serum lithium concentrations and toxicity.

Note: Diovan (Valsartan) is a prescription-only medication. Treatment, dose adjustments, and monitoring should strictly follow the guidance of a licensed healthcare professional.