Irbesartan Cristers (Irbesartan)

Irbesartan is an angiotensin II receptor blocker used to manage conditions related to the renin‑angiotensin system.

• Hypertension: lowers systolic and diastolic blood pressure, reducing cardiovascular risk.
• Diabetic nephropathy: slows progression of kidney damage in patients with type 2 diabetes.
• Heart failure: improves symptoms and reduces hospitalization in chronic heart failure patients.

• Irbesartan selectively antagonizes the angiotensin II type 1 (AT1) receptor, preventing angiotensin II from binding and activating the receptor. This inhibition blocks the vasoconstrictive, aldosterone‑secreting, and sympathetic‑stimulating effects of angiotensin II, leading to vasodilation, reduced sodium and water retention, and decreased peripheral resistance, which collectively lower arterial pressure while sparing AT2 receptors.

Irbesartan may cause a range of adverse reactions, varying from mild to serious.

Common Side Effects

• Dizziness or light‑headedness, particularly after initiating therapy.
• Headache, which may be mild to moderate in intensity.
• Fatigue or a general feeling of tiredness.
• Elevated blood potassium (hyperkalaemia), detectable on laboratory testing.
• Nasal congestion or other upper‑respiratory symptoms.
• Diarrhea or mild abdominal discomfort.

Serious or Rare Side Effects

• Angio‑edema involving the face, lips, tongue or airway, which can be life‑threatening.
• Acute kidney injury or a marked increase in serum creatinine indicating worsening renal function.

When prescribing Irbesartan, clinicians should consider several precautionary measures to ensure safe use.

• Monitor blood pressure: check baseline and periodic readings to avoid hypotension.
• Assess renal function: evaluate serum creatinine and eGFR before starting and during therapy.
• Check serum potassium: hyperkalaemia risk requires periodic potassium monitoring.
• Use caution in patients with hepatic impairment: dose adjustment may be needed.
• Avoid in pregnancy: drug is contraindicated in the second and third trimesters (Category D).
• Store at ambient temperature: keep below 25 °C, in the original container, protected from moisture.

Irbesartan can interact with other medicines, altering its effectiveness or increasing adverse effect risk.

Major Interactions (Avoid)

• Concomitant use with aliskiren in patients with diabetes or renal impairment.
• Potassium‑sparing diuretics or supplements that may cause severe hyperkalaemia.
• Dual renin‑angiotensin system blockade (e.g., ACE inhibitors) due to risk of renal dysfunction.

Moderate Interactions (Monitor Closely)

• Non‑steroidal anti‑inflammatory drugs (NSAIDs) that can reduce antihypertensive effect and impair renal function.
• Lithium: increased lithium levels may lead to toxicity.
• Certain anti‑arrhythmic agents (e.g., amiodarone) that may affect plasma concentrations.