IRBESARTAN

IRBESARTAN (ir-be-sar'tan) Avapro Classifications: angiotensin ii receptor antagonist; antihypertensive; Therapeutic: antihypertensive; angiotensin ii receptor antagonist Prototype: Losartan Pregnancy Category: C first trimester; D second and third trimester

Availability

75 mg, 150 mg, 300 mg tablets

Action

Irbesartan is an angiotensin II receptor (type AT₁) antagonist. Angiotensin II is a hormone of the renin–angiotensin–aldosterone system. Irbesartan selectively blocks the binding of angiotensin II to the AT₁ receptors found in many tissues (e.g., vascular smooth muscle, adrenal glands), resulting in vasodilation of vascular smooth muscle.

Therapeutic Effect

Binding to the angiotensin receptors results in blocking the vasoconstricting and aldosterone-secreting effects of angiotensin II, thus resulting in an antihypertensive effect.

Uses

Hypertension, treatment of diabetic nephropathy in patients with hypertension and type 2 diabetes.

Unlabeled Uses

CHF.

Contraindications

Hypersensitivity to irbesartan, losartan, or valsartan; hypovolemia; pregnancy (category C first trimester, category D second and third trimester), lactation, children.

Cautious Use

Patients on diuretics, arterial stenosis of the renal artery, hepatic disease; severe CHF, African American patients.

Route & Dosage

Hypertension Adult: PO Start with 150 mg once daily, may increase to 300 mg/d

Administration

Oral

• Correct volume depletion prior to initiation of therapy to prevent hypotension. Titrate daily dose up to 300 mg; larger doses, however, are not likely to provide additional benefit.

Adverse Effects (≥1%)

Body as a Whole: Edema, fatigue, pain. CNS: Dizziness, headache, anxiety, nervousness. CV: Tachycardia, chest pain. GI: Diarrhea, dyspepsia, nausea, vomiting, abdominal pain. Respiratory: Upper respiratory infection, cough, sinus disorder, pharyngitis, rhinitis. Skin: Rash. Other: UTI, hepatitis.

Pharmacokinetics

Absorption: Rapidly absorbed from GI tract, 60–80% bioavailability. Distribution: 90% protein bound. Metabolism: In the liver primarily by CYP2C9. Elimination: Primarily in feces. Half-Life: 11–15 h.

Nursing Implications

Assessment & Drug Effects

• Monitor for therapeutic effectiveness: Maximum pressure lowering effect may not be evident for 6–12 wk; indicated by decreases in systolic and diastolic BP.
• Monitor BP periodically; trough readings, just prior to the next scheduled dose, should be made when possible.
• Lab tests: Monitor periodically BUN and creatinine, serum potassium, and CBC with differential.

Patient & Family Education

• Inform physician immediately if you become pregnant.
• Notify physician of episodes of dizziness, especially when making position changes.

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Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug