Losartan Potassium

losartan potassium (low sar' tan) Cozaar Pregnancy Category C (first trimester) Pregnancy Category D (second and third trimesters) Drug classes

Angiotensin II receptor blocker (ARB) Antihypertensive Therapeutic actions

Selectively blocks the binding of angiotensin II to specific tissue receptors found in the vascular smooth muscle and adrenal gland; this action blocks the vasoconstriction effect of the renin-angiotensin system as well as the release of aldosterone leading to decreased blood pressure. Indications

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Treatment of hypertension, alone or in combination with other antihypertensive agents Treatment of diabetic neuropathy with an elevated serum creatinine and proteinuria in patients with type 2 (non–insulin-dependent) diabetes and a history of hypertension

Contraindications and cautions

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Contraindicated with hypersensitivity to losartan, pregnancy (use during the second or third trimester can cause injury or even death to the fetus), lactation. Use cautiously with hepatic or renal dysfunction, hypovolemia.

Available forms

Tablets—25, 50, 100 mg Dosages ADULTS

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Hypertension: Starting dose of 50 mg PO daily. Patients on diuretics or hypovolemic patients may only require 25 mg daily. Dosage ranges from 25– 100 mg PO given once or twice a day have been used. Diabetic neuropathy: 50 mg/day PO once daily; may be increased to 100 mg/day once daily based on blood pressure response. Stroke reduction: 50 mg/day PO with 12.5 mg/day hydrochlorothiazide may be increased to 100 mg/day PO with 25 mg/day hydrochlorothiazide if needed.

PEDIATRIC PATIENTS

Safety and efficacy not established. Pharmacokinetics Route Oral

Onset Varies

Peak 1–3 hr

Metabolism: Hepatic; T1/2: 2 hr, then 6–9 hr Distribution: Crosses placenta; enters breast milk Excretion: Feces and urine Adverse effects

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CNS: Headache, dizziness, syncope, insomnia CV: Hypotension Dermatologic: Rash, urticaria, pruritus, alopecia, dry skin GI: Diarrhea, abdominal pain, nausea, constipation, dry mouth Respiratory: URI symptoms, cough, sinus disorders Other: Back pain, fever, gout, muscle weakness

Interactions

Drug-drug • Decreased serum levels and effectiveness if taken concurrently with phenobarbital • Losartan is converted to an active metabolite by cytochrome P450-3A4. Drugs that inhibit 3A4 (ketoconazole, fluconazole, diltiazem) may decrease the antihypertensive effects of losartan Nursing considerations Assessment

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History: Hypersensitivity to losartan, pregnancy, lactation, hepatic or renal dysfunction, hypovolemia Physical: Skin lesions, turgor; T; reflexes, affect; BP; R, respiratory auscultation; liver and kidney function tests

Interventions

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Administer without regard to meals. Ensure that patient is not pregnant before beginning therapy, suggest using barrier birth control while using losartan; fetal injury and deaths have been reported. Find an alternative method of feeding the baby if given to a nursing mother. Depression of the renin-angiotensin system in infants is potentially very dangerous. Alert surgeon and mark patient's chart with notice that losartan is being taken. The blockage of the renin-angiotensin system following surgery can produce problems. Hypotension may be reversed with volume expansion. Monitor patient closely in any situation that may lead to a decrease in blood pressure secondary to reduction in fluid volume—excessive perspiration, dehydration, vomiting, diarrhea—excessive hypotension can occur.

Teaching points

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Take drug without regard to meals. Do not stop taking this drug without consulting your health care provider.

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Use a barrier method of birth control while on this drug; if you become pregnant or desire to become pregnant, consult with your health care provider. These side effects may occur: Dizziness (avoid driving a car or performing hazardous tasks); headache (request medications); nausea, vomiting, diarrhea (proper nutrition is important, consult with your dietitian to maintain nutrition); symptoms of upper respiratory tract infection, cough (do not self-medicate; consult your health care provider if uncomfortable). Report fever, chills, dizziness, pregnancy.

Adverse effects in Italic are most common; those in Bold are life-threatening.