losartan potassium

Action

Blocks vasoconstricting and aldosterone-secreting effects of angiotensin II at various receptor sites, including vascular smooth muscle and adrenal glands. Also increases urinary flow and enhances excretion of chloride, magnesium, calcium, and phosphate.

Availability

Tablets: 25 mg, 50 mg, 100 mg

Indications and dosages

➣ Hypertension

Adults: Initially, 50 mg/day P.O.; range is 25 to 100 mg/day as a single dose or in two divided doses. May be used alone or with other drugs.

Children ages 6 and older: 0.7 mg/kg P.O. daily, up to total of 50 mg

➣ To prevent cerebrovascular accident (stroke) in hypertensive patients with left ventricular hypertrophy (LVH)

Adults: Initially, 50 mg P.O. daily, increased to 100 mg P.O. daily. May be given concurrently with hydrochlorothiazide.

➣ Nephropathy in patients with type 2 diabetes

Adults: 50 mg/day P.O.; increase to 100 mg/day based on blood pressure response.

Dosage adjustment

• Hepatic impairment

• Concurrent diuretic therapy

Contraindications

• Hypersensitivity to drug or its components

• Pregnancy (second and third trimesters)

Precautions

Use cautiously in:

• heart failure, renal or hepatic impairment, obstructive biliary disorders

• high-dose diuretic therapy

• black patients

• pregnant patients (first trimester) or breastfeeding patients

• children younger than age 6 (safety not established).

Administration

• Administer with or without food.

• Know that if drug efficacy (measured at trough) is inadequate with once-daily dosing, prescriber may switch to twice-daily regimen using same or higher daily dosage.

• Be aware that drug may take 3 to 6 weeks to reach maximal efficacy.

Adverse reactions

CNS: dizziness, insomnia, headache, asthenia, fatigue

CV: hypotension

EENT: sinus disorders

GI: nausea, vomiting, diarrhea, dyspepsia, abdominal pain

Metabolic: hyperkalemia

Musculoskeletal: joint pain, back pain, muscle cramps

Respiratory: symptoms of upper respiratory infection, dry cough

Other: hypersensitivity reactions including angioedema

Interactions

Drug-drug. Diuretics, other antihypertensives: increased risk of hypotension

Fluconazole: inhibited losartan metabolism, increased antihypertensive effects

Indomethacin: decreased losartan effects

Lithium: decreased lithium metabolism

Nonsteroidal anti-inflammatory drugs: decreased renal function

Potassium-sparing diuretics, potassium supplements: hyperkalemia

Rifamycins: enhanced losartan metabolism, decreased antihypertensive effects

Drug-diagnostic tests. Albumin: increased level

Drug-food. Salt substitutes containing potassium: hyperkalemia

Patient monitoring

See Watch for angioedema and other hypersensitivity reactions.

• Monitor blood pressure to evaluate drug efficacy.

• Assess liver and kidney function tests and electrolyte levels.

• Stay alert for oliguria, progressive azotemia, and renal failure in patients with severe heart failure whose renal function depends on the renin-angiotensin-aldosterone system.

• Know that in black patients, losartan and other ACE inhibitors may be ineffective when used alone. Drug isn't indicated for stroke prevention in black hypertensive patients with LVH.

• Be aware that drug may cause fetal injury or death when used during second or third trimester of pregnancy.

Patient teaching

• Instruct patient to avoid potassium supplements and salt substitutes containing potassium, unless directed by prescriber.

See Caution female patient not to take drug during second or third trimester of pregnancy. Advise her to contact prescriber immediately if she suspects pregnancy.

• Tell female patient to discuss breastfeeding with prescriber before taking.

See Instruct patient to immediately report hypersensitivity reactions, especially lip or eyelid swelling, throat tightness, and difficulty breathing.

• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs, tests, and foods mentioned above.