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Angiotensin II Receptor Blocker (ARB) — Hypertension / Raynaud's / Marfan Syndrome Pregnancy: Contraindicated in 2nd/3rd trimester — fetotoxic (renal dysgenesis, oligohydramnios, skull hypoplasia); use with caution in 1st trimester

Losartan

Brand names: Cozaar

Adult dose

Dose: Hypertension: 50 mg once daily; Raynaud's (off-label): 50 mg once daily; Marfan syndrome: 50–100 mg once daily
Route: Oral
Frequency: Once daily
Max: 100 mg/day
Losartan has intrinsic uricosuric properties (blocks URAT1 renal urate transporter) — useful in hypertensive patients with gout. In Raynaud's: RAAS blockade reduces vasospasm. In Marfan syndrome: reduces aortic root dilation rate (TGF-beta pathway modulation).

Paediatric dose

Dose: 0.7 mg/kg mg/kg
Route: Oral
Frequency: Once daily
Max: 50 mg/day (child 6–18 years)
BNFc: licensed for hypertension in children ≥6 years weighing >20 kg

Dose adjustments

Renal

No dose adjustment for mild-moderate renal impairment; avoid if CrCl <20 mL/min or in bilateral renal artery stenosis

Hepatic

Reduce dose — hepatic conversion to active metabolite (EXP3174); start at 25 mg in hepatic impairment

Paediatric weight-based calculator

BNFc: licensed for hypertension in children ≥6 years weighing >20 kg

Clinical pearls

  • Only ARB with clinically relevant uricosuric activity — useful in hypertensive patients who also have gout or hyperuricaemia; other ARBs lack this property
  • LIFE trial: losartan superior to atenolol for CV outcomes in hypertensive patients with LVH — particularly reduced stroke
  • Marfan syndrome: COMPARE trial showed losartan equivalent to atenolol for aortic root dilation control — offers alternative to beta-blockade
  • Does not cause cough (unlike ACE inhibitors — no bradykinin accumulation) — preferred switch when ACE inhibitor cough intolerable
  • Active metabolite EXP3174 is 10–40× more potent than losartan — hepatic conversion essential for efficacy

Contraindications

  • Bilateral renal artery stenosis
  • Pregnancy (second/third trimester — fetotoxic)
  • Concurrent aliskiren in diabetes/renal impairment
  • Hyperkalaemia
  • Severe hepatic impairment

Side effects

  • Hyperkalaemia
  • Hypotension (first dose)
  • Renal impairment
  • Dizziness
  • Hyperuricaemia reduction (beneficial uricosuric)
  • Diarrhoea
  • Dry cough much less common than ACE inhibitors

Interactions

  • Potassium-sparing diuretics/supplements — hyperkalaemia
  • NSAIDs — reduce antihypertensive effect, additive renal toxicity
  • Lithium — increases lithium levels
  • Aliskiren — avoid in diabetes/renal impairment (dual RAAS blockade)

Monitoring

  • Blood pressure
  • Renal function and electrolytes (1–2 weeks after initiation or dose change)
  • Serum potassium
  • Uric acid (if gout history)

Reference: BNFc; BNF 90; LIFE Trial; COMPARE Trial (Marfan); NICE NG136 (Hypertension); BSR/BHPR Raynaud's Guidelines. Verify against your local formulary and the latest BNF before prescribing.

Related

Curated clinical cross-links plus same-class fallbacks.

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