Losartan

Indications

Oral
Hypertension
Adult: 50 mg once daily, increased to 100 mg daily as a single dose or in 2 divided doses if needed.
Child: ≥6 yr: Initially 700 mcg/kg increased to a maximum of 50 mg once daily if needed.
Elderly: >75 yr: Initally, 25 mg once daily.

CrCl (ml/min)	Dosage Recommendation
<20	Initially 25 mg once daily.

Hepatic impairment: Initially, 25 mg once daily
Oral
Diabetic nephropathy in Type 2 diabetes mellitus
Adult: 50 mg once daily, increased to 100 mg daily as a single dose or in 2 divided doses if needed.
Elderly: >75: Initially 25 mg once daily.
Renal impairment: CrCl <20 ml/min: Initially 25 mg once daily.

CrCl (ml/min)	Dosage Recommendation
<20	Initially 25 mg once daily.

Hepatic impairment: Initially 25 mg once daily.

Special Populations: Patients with moderate to severe renal impairment (CrCl <20 mL/min) or intravascular fluid depletion: Initially, 25 mg once daily. Reduce dose in hepatic impairment.

Contraindications

Pregnancy, lactation; children with CrCl <30 ml/min/1.73m².

Warnings / Precautions

Volume-depleted patients including patients on diuretics and salt restriction; renal artery stenosis; elderly; renal or hepatic impairment. Monitor serum-potassium concentration.

Adverse Reactions

Headache, dizziness, back pain, myalgia, respiratory tract disorders, asthenia/fatigue, first dose hypotension, rash, angioedema, neutropenia, GI disturbances, transient elevation of liver enzymes, impaired renal function, taste disturbances and hyperkalaemia.

Drug Interactions

Hypotensive effect of losartan potentiated by diuretics and other antihypertensives. Risk of hyperkalaemia increases with concomitant ACE inhibitors, ciclosporin, potassium-sparing diuretics and K supplements. Hypotensive effect may be antagonised and increased risk of renal impairment when used with NSAIDs.
Potentially Fatal: Risk of lithium toxicity with losartan use.
See Below for More losartan Drug Interactions

Mechanism of Actions

Losartan is an angiotensin II receptor antagonist. The drug and its active metabolite selectively block the vasoconstrictor and aldosterone-secreting effects of angiotensin II by selectively antagonising its binding to AT₁ receptors.
Absorption: Readily absorbed from GI tract with peak plasma concentrations of losartan after around 1 hr and its active metabolite after 3-4 hr.
Distribution: 98% plasma protein bound.
Metabolism: Hepatic metabolism principally by isoenzymes CYP3A4 and 2C9.
Excretion: Excreted in faeces and urine as metabolites and unchanged drug. Terminal elimination half life of 2 hr (losartan) and 6-9 hr (active metabolite).