Irbésartan/Hydrochlorothiazide Cristers (Hydrochlorothiazide, Irbesartan)

Irbesartan/Hydrochlorothiazide is an antihypertensive combination that lowers elevated blood pressure through dual mechanisms.

• Hypertension: provides sustained reduction of systolic and diastolic blood pressure in patients with primary hypertension.
• Essential hypertension: improves blood‑pressure control when monotherapy is insufficient.
• High blood pressure: assists in achieving target blood‑pressure goals as part of a comprehensive treatment plan.

• Irbesartan selectively blocks AT1 receptors, preventing angiotensin II‑mediated vasoconstriction and aldosterone release, which lowers peripheral resistance. Hydrochlorothiazide inhibits NaCl reabsorption in the distal convoluted tubule, increasing urinary sodium and water excretion, thereby reducing plasma volume. The combined actions result in additive blood‑pressure lowering effects.

Adverse reactions may vary in frequency and severity.

Common Side Effects

• Dizziness or light‑headedness
• Headache
• Fatigue or weakness
• Increased urinary frequency
• Electrolyte disturbances (e.g., low potassium)
• Mild gastrointestinal discomfort

Serious or Rare Side Effects

• Severe dehydration or electrolyte imbalance
• Acute kidney injury or worsening renal function
• Hyperkalemia or severe hypokalemia
• Angioedema or severe allergic reaction
• Significant hypotension leading to syncope
• Blood dyscrasias such as agranulocytosis

Patients should be monitored for safety and appropriate use.

• Blood pressure monitoring: check regularly to ensure therapeutic response.
• Renal function assessment: evaluate serum creatinine and eGFR before and during therapy.
• Electrolyte surveillance: monitor potassium and sodium levels, especially with concomitant drugs.
• Pregnancy avoidance: contraindicated in pregnancy due to fetal risk.
• Elderly caution: start at lower dose and monitor for orthostatic hypotension.
• Store at room temperature: keep in original container, protect from moisture and direct sunlight.

Irbesartan/Hydrochlorothiazide may interact with several medicines.

Major Interactions (Avoid)

• Aliskiren: combined use can increase risk of renal impairment and hyperkalemia.
• Lithium: thiazide component may raise lithium levels, leading to toxicity.
• ACE inhibitors or other ARBs: additive effects on potassium and renal function.
• Potassium‑sparing diuretics or supplements: risk of hyperkalemia.
• NSAIDs: may blunt antihypertensive effect and worsen renal function.

Moderate Interactions (Monitor Closely)

• Other diuretics: monitor electrolytes and volume status.
• Antihypertensive agents (beta‑blockers, calcium channel blockers): may enhance blood‑pressure lowering.
• CYP2C9 inhibitors (e.g., fluconazole): can increase irbesartan plasma concentrations.
• Antidiabetic drugs: diuretic‑induced changes in glucose may require dose adjustment.