| Definition | Angiotensin II receptor blocker (ARB) used primarily for hypertension. | ||
|---|---|---|---|
| Pharmacological Classification | ARB (selective AT1 receptor antagonist) | Mechanism of Action | Blocks angiotensin II at AT1 receptor → ↓ vasoconstriction, ↓ aldosterone secretion → ↓ blood pressure, ↓ afterload, renal protection (less potent proteinuria-reduction vs ACEi). |
| Monitoring Parameters | • BP (clinic + home) • Renal function: SCr & eGFR baseline and within 2–4 weeks of initiation • Potassium levels baseline and periodically • Assess for chronic diarrhea (enteropathy red flag) |
Clinical Tips | • Best ARB choice for once-daily BP suppression (longer t½ vs losartan) • Avoid in chronic diarrhea—switch to losartan/valsartan if enteropathy suspected • When BP remains uncontrolled → combine with thiazide (chlorthalidone) or CCB (amlodipine) |
| Indications | • Hypertension (first-line) • Renal protection in diabetes/CKD (adjunct) • Heart failure (less preferred vs ACEi/valsartan) • LVH (secondary benefit) |
Dosage | Adult: 20–40 mg PO once daily (start 20 mg; max 40 mg/day) Pediatric (6–16 yrs): 10 mg PO daily (20 mg if ≥35 kg; max 40 mg/day) Renal dose: No adjustment (CrCl ≥20 mL/min) — caution in severe impairment Hepatic impairment: No formal adjustment but start low |
| Contraindications | • Pregnancy (fetal toxicity) • Bilateral renal artery stenosis • Severe hypotension • Hypersensitivity |
Adverse Drug Reaction | Common: Dizziness, hyperkalemia, hypotension, fatigue Less common: ↑ serum creatinine, renal impairment Rare but serious: Sprue-like enteropathy (chronic diarrhea, weight loss), angioedema (rare vs ACEi) |
| Counselling | • Take once daily, same time each day • May take 2–4 weeks for full BP effect • Avoid potassium supplements or salt substitutes • Stop immediately if severe diarrhea/weight loss develops (sprue-like enteropathy risk) • Avoid in pregnancy—inform provider if planning pregnancy |
Drug–Drug Interaction | • ACEi/Aliskiren → ↑ risk of renal dysfunction & hyperkalemia (avoid dual RAS blockade) • NSAIDs → blunt antihypertensive effect; ↑ AKI risk • K-sparing diuretics, K supplements → hyperkalemia • Lithium → ↑ lithium levels |
| Pharmacokinetics | Bioavailability: 26% Onset: ~1 week; full effect ~2–4 weeks Peak: 1–2 hrs T½: ~13 hrs (allows once-daily dosing) Protein binding: ~99% Metabolism: Limited hepatic metabolism Elimination: Fecal mostly |
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