IRBESARTAN

Clinical safety rating: avoid

Contraindicated (not allowed)

How it works

Irbesartan is an angiotensin II receptor blocker (ARB) that selectively and competitively inhibits the binding of angiotensin II to AT1 receptors in vascular smooth muscle and adrenal gland, thereby blocking vasoconstriction and aldosterone secretion.

What the body does with it

Metabolism	Irbesartan is primarily metabolized by CYP2C9 (with minor contribution by CYP3A4) via glucuronidation and oxidation to inactive metabolites.
Excretion	Irbesartan is primarily eliminated via biliary/fecal excretion (approximately 80%) and renal excretion (approximately 20%).
Half-life	The terminal elimination half-life of irbesartan is 11–15 hours, supporting once-daily dosing.
Protein binding	Irbesartan is approximately 90% bound to plasma proteins, primarily albumin and alpha-1-acid glycoprotein.
Volume of Distribution	The volume of distribution is 53–93 L (approximately 0.7 L/kg), indicating extensive distribution into tissues.
Bioavailability	Oral bioavailability of irbesartan is 60–80%.
Onset of Action	Following oral administration, the antihypertensive effect begins within 1–2 hours.
Duration of Action	Duration of action is approximately 24 hours, allowing once-daily dosing; maximal blood pressure reduction is typically achieved after 2–4 weeks of therapy.

Classification & Brands

Dosing & administration

150 mg orally once daily; may increase to 300 mg once daily if needed.

Dosage form	TABLET
Renal impairment	GFR 30-89 mL/min: No adjustment needed. GFR <30 mL/min: Limited data; cautiously use lower starting dose of 75 mg once daily.
Liver impairment	Child-Pugh Class A or B: No adjustment needed. Child-Pugh Class C: No data; use with caution.
Pediatric use	Children 6-12 years: 75 mg orally once daily; may increase to 150 mg once daily. Children 13-17 years: 150 mg orally once daily; may increase to 300 mg once daily.
Geriatric use	Start at 75 mg orally once daily; titrate slowly due to potential renal impairment and hypotension.

Use during pregnancy

1st trimester	Consult provider
2nd trimester	Consult provider
3rd trimester	Consult provider

Clinical note

NSAIDs may diminish the antihypertensive effect Lithium levels may be increased Use in pregnancy can cause injury and death to the developing fetus.

Breastfeeding

No human data on irbesartan in breast milk; animal data indicate low excretion. M/P ratio unknown. Due to potential for adverse effects on neonatal renal function, decision to breastfeed requires consideration of maternal need and infant monitoring.

Teratogenic Risk

First trimester: limited human data suggests low risk of major malformations; angiotensin receptor blocker (ARB) exposure is associated with increased risk of renal and cardiovascular malformations compared to no exposure. Second and third trimesters: fetal renal hypoperfusion, oligohydramnios, anuria, renal failure, skull ossification defects, hypotension, and death. Risk is dose-dependent and potentially reversible if discontinued early.

Warnings & precautions

■ FDA Black Box Warning

None.

Side Effect Profile

Common Effects	diabetic nephropathy
Serious Effects

Absolute Contraindications

["Concomitant use with aliskiren in patients with diabetes mellitus","History of hypersensitivity to irbesartan or any component of the formulation"]

Clinical Precautions

Precautions

["Fetal toxicity (avoid use in pregnancy; discontinue if pregnancy detected)","Hypotension in volume- or salt-depleted patients","Risk of acute renal insufficiency in patients with renal artery stenosis","Hyperkalemia, especially in patients with renal impairment or on potassium-sparing diuretics","Avoid concomitant use with aliskiren in patients with diabetes mellitus"]

Clinical Tips & Counseling

Drug interactions

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