Losartan: clinical use

Prescribing considerations

• Assess volume depletion, hypotension, renal function, electrolyte disturbance and concomitant medicines before initiation.
• Use caution with renal artery stenosis, renal impairment, heart failure, significant aortic or mitral stenosis, obstructive hypertrophic cardiomyopathy or previous angioedema.
• Losartan exposure is increased in hepatic impairment; severe hepatic impairment is contraindicated.
• Renin–angiotensin system blockers may produce a smaller average blood-pressure response in Black patients with hypertension.
• Review treatment promptly during acute illness associated with dehydration or possible renal compromise.

Contraindications and cautions

• Hypersensitivity to losartan or a product excipient.
• Second or third trimester of pregnancy.
• Severe hepatic impairment.
• Aliskiren co-administration in diabetes mellitus or renal impairment with GFR below 60 mL/min/1.73 m².

Monitoring

• Before treatment: blood pressure, estimated GFR or serum creatinine, potassium and sodium.
• Recheck blood pressure, renal function and electrolytes after initiation or treatment changes, with earlier or more frequent review in higher-risk patients.
• Continue periodic renal function, sodium and potassium monitoring once stable and repeat testing during acute illness or possible renal compromise.
• Investigate clinically important rises in potassium or creatinine and review dehydration, renal artery disease and interacting medicines.

Clinical pharmacology

Losartan is an oral selective AT1-receptor antagonist. It undergoes first-pass metabolism, mainly through CYP2C9, to a more potent active carboxylic-acid metabolite. Losartan and its active metabolite are highly protein bound; neither is removed by haemodialysis.

Formulation and product differences

• The selected products are lactose-containing film-coated tablets.
• The selected 25 mg tablet is white to off-white, oval and marked “J” and “25”.
• The selected 50 mg tablet is white to off-white, oval, scored on one side and marked “J” and “50”; check the specific product information before splitting.
• Special-order losartan liquids may be available for swallowing difficulties; crushing film-coated tablets is off-label.

Tablet

Route: Oral

Strengths: 12.5 mg, 25 mg, 50 mg, 100 mg