Irbesartan

Irbesartan is an angiotensin II receptor antagonist that blocks the vasoconstricting and aldosterone-secreting effects of angiotensin II by binding to AT1 receptors. It relaxes blood vessels to lower blood pressure and helps preserve renal function in patients with type 2 diabetes. Irbesartan is mainly metabolised by CYP2C9 and to a lesser extent by glucuronidation.

• Essential hypertension
• Treatment of renal disease in patients with hypertension and type 2 diabetes mellitus

Adult Dose (Oral):

• Hypertension: 150 mg once daily; may increase to 300 mg once daily if needed
• Intravascular volume depletion: Initially, 75 mg once daily
• Elderly (>75 years): Initially, 75 mg once daily
• Diabetic nephropathy in Type 2 diabetes: Initially, 75-150 mg once daily; may increase to 300 mg once daily if needed

Child Dose (≥12 years): 150 mg/day initially; may increase to 300 mg/day

Renal Dose: Haemodialysis: 75 mg once daily initially; mild-to-severe renal impairment: no dosage adjustment necessary (unless hypovolemic)

Common Side Effects:

• Dizziness
• Increased potassium level in blood
• Headache
• Fatigue
• Nausea
• Vomiting

Less Common: Anxiety, Nervousness, Belching, Heartburn, Stomach discomfort, Diarrhea, Muscle or bone pain, Unusual tiredness

Precautions:

• It is not known whether Irbesartan alters ability to drive; do not drive if you experience symptoms affecting concentration and reaction
• May cause dizziness for first few days; rise slowly from sitting or lying position
• Intravascular volume depletion: caution in patients volume and/or sodium depleted by vigorous diuretic therapy, dietary salt restriction, diarrhea or vomiting
• Caution in renal artery stenosis, aortic or mitral stenosis, obstructive hypertrophic cardiomyopathy
• Contraindicated in pregnancy and lactation

Contraindications:

• Hypersensitivity
• Pregnancy
• Lactation
• Concomitant use with aliskiren in patients with diabetes and renal impairment (GFR <60 mL/min)

Drug Interactions:

• May antagonise hypotensive effect and increase risk of nephrotoxicity with NSAIDs
• May increase serum lithium levels and toxicity
• Increased risk of hyperkalaemia with K-sparing diuretics, K supplements or K-containing salt substitutes
• May increase nephrotoxic, hyperkalaemic and hypotensive effect with aliskiren (Potentially Fatal)

Food Interactions: Irbesartan may cause excessive drowsiness with alcohol.

Use in Pregnancy: Unsafe; second and third trimesters may cause fetal or neonatal renal failure, fetal skull hypoplasia and fetal death; avoid in first trimester; discontinue as soon as pregnancy is diagnosed.

Use in Lactation: Unsafe; it is not known whether irbesartan is excreted in human milk; excreted in milk of lactating rats.

Renal Impairment: No dosage adjustment necessary in renal impairment; haemodialysis patients: 75 mg once daily initially; caution in severe renal impairment.

Hepatic Impairment: No dosage adjustment necessary in mild to moderate hepatic impairment; no clinical experience in severe hepatic impairment.

Overdose: Doses up to 900 mg/day for 8 weeks revealed no toxicity; most likely manifestations: hypotension and tachycardia; bradycardia may also occur; induction of emesis and/or gastric lavage; activated charcoal may be useful; not removed by haemodialysis.