Irbesartan Cristers (Irbesartan)

Irbesartan is indicated for conditions that involve the renin‑angiotensin system and related cardiovascular or renal disease.

• Hypertension: reduces systolic and diastolic blood pressure, helping to prevent cardiovascular complications.
• Diabetic nephropathy: slows the progression of kidney damage in patients with type 2 diabetes.
• Heart failure (off‑label): may improve symptoms and reduce hospitalisation when used under specialist supervision.

• Irbesartan selectively blocks angiotensin II type 1 (AT1) receptors on vascular smooth muscle and adrenal cells. By preventing angiotensin II binding, it inhibits vasoconstriction and aldosterone secretion, leading to vasodilation, reduced sodium and water retention, and ultimately lower blood pressure and decreased workload on the heart and kidneys.

Irbesartan may be associated with a range of adverse reactions, which are categorised by frequency and severity.

Common Side Effects

• Dizziness: sensation of light‑headedness, especially after standing.
• Headache: mild to moderate pain in the head region.
• Fatigue: feeling unusually tired or weak.
• Hyperkalaemia: elevated potassium levels, often mild.

Serious or Rare Side Effects

• Angioedema: swelling of face, lips, tongue or throat that may compromise breathing.
• Severe hyperkalaemia: markedly high potassium that can affect heart rhythm.
• Acute renal failure: sudden decline in kidney function, indicated by rising creatinine.
• Hepatic injury: abnormal liver enzymes or jaundice.
• Neutropenia: low white‑blood‑cell count increasing infection risk.

Before initiating therapy, clinicians should assess individual risk factors and monitor relevant laboratory parameters.

• Monitor blood pressure: adjust dose to achieve target values.
• Assess renal function: check serum creatinine and eGFR before and during treatment.
• Check serum potassium: avoid hyperkalaemia, especially when combined with potassium‑sparing agents.
• Avoid use in pregnancy: drug is contraindicated due to potential fetal harm.
• Use caution in hepatic impairment: consider dose adjustment or close monitoring.
• Store at ambient temperature: keep in original pack, protect from moisture.

Irbesartan can interact with several medicines, requiring either avoidance or careful monitoring.

Major Interactions (Avoid)

• Aliskiren in diabetic patients: increased risk of renal impairment and hyperkalaemia.
• ACE inhibitors: additive effects on potassium and renal function, may cause severe hyperkalaemia.
• Potassium‑sparing diuretics: heightened risk of dangerous hyperkalaemia.

Moderate Interactions (Monitor Closely)

• Thiazide diuretics: may enhance antihypertensive effect, requiring dose adjustment.
• CYP2C9 inhibitors (e.g., fluconazole): can raise irbesartan plasma concentrations.
• Other antihypertensives: additive blood‑pressure lowering effect, monitor for hypotension.