Irbesartan/Hydrochlorothiazide Viatris (Hydrochlorothiazide, Irbesartan)

Irbesartan/Hydrochlorothiazide acts on the renin‑angiotensin‑aldosterone system and renal sodium handling to lower blood pressure.

• Essential hypertension: reduces systolic and diastolic pressure in patients with primary high blood pressure.
• Resistant hypertension: adds a diuretic effect to improve control when an ARB alone is insufficient.
• Hypertension with fluid retention: promotes diuresis to manage volume overload while lowering blood pressure.

• Irbesartan selectively blocks the angiotensin II type 1 (AT1) receptor, preventing vasoconstriction and aldosterone release. Hydrochlorothiazide inhibits sodium‑chloride reabsorption in the distal convoluted tubule, increasing urinary excretion of water and electrolytes, which lowers plasma volume. The combined actions produce additive reductions in systemic vascular resistance and circulating volume, resulting in lowered arterial pressure.

Common Side Effects

• Dizziness or light‑headedness, especially after the first dose.
• Headache.
• Increased urination or nocturia.
• Mild electrolyte disturbances such as low potassium.
• Fatigue or weakness.
• Mild gastrointestinal upset.

Serious or Rare Side Effects

• Severe hypotension leading to fainting.
• Acute kidney injury or worsening renal function.
• Hyperkalemia, particularly when combined with potassium‑sparing agents.
• Allergic reactions including rash, angioedema, or anaphylaxis.
• Pancreatitis.
• Significant liver enzyme elevations.

Before initiating therapy, clinicians should evaluate patient history and monitor relevant parameters.

• Blood pressure monitoring: ensure adequate control and avoid excessive drops.
• Renal function assessment: check serum creatinine and eGFR periodically.
• Electrolyte surveillance: monitor potassium and sodium levels, especially in patients on other diuretics.
• Caution in elderly patients: start at lower doses due to increased sensitivity.
• Pregnancy and lactation: avoid use unless clearly indicated, as safety data are limited.
• Store at ambient temperature: keep in the original container, protect from moisture and direct sunlight.

Irbesartan/Hydrochlorothiazide may interact with several medicines; careful review is recommended.

Major Interactions (Avoid)

• Aliskiren combined with an ARB: risk of renal impairment and hyperkalemia.
• Potassium‑sparing diuretics or supplements: may cause dangerous hyperkalemia.
• Non‑steroidal anti‑inflammatory drugs (NSAIDs): can blunt antihypertensive effect and affect renal function.
• Lithium: increased lithium levels and toxicity risk.

Moderate Interactions (Monitor Closely)

• ACE inhibitors or other ARBs: additive blood‑pressure lowering, monitor for hypotension.
• Other thiazide or loop diuretics: risk of excessive diuresis and electrolyte loss.
• Antidiabetic agents: blood‑glucose may improve, requiring dose adjustment.
• CYP3A4 inhibitors (e.g., ketoconazole): may increase irbesartan plasma concentrations.
• Antihypertensive combinations (beta‑blockers, calcium channel blockers): monitor for additive hypotensive effect.