losartan potassium

losartan potassium

(low sar' tan)

Cozaar

Pregnancy Category C (first trimester)

Pregnancy Category D (second and third trimesters)

Drug classes

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 BP.

Indications

·        Treatment of hypertension, alone or in combination with other antihypertensives

·        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

·        Reduction of the risk of stroke in patients with hypertension and left ventricular hypertrophy

Contraindications and cautions

·        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

·        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 BP 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	Onset	Peak
Oral	Varies	1–3 hr

Metabolism: Hepatic; T_1/2: 2 hr, then 6–9 hr

Distribution: Crosses placenta; enters breast milk

Excretion: Feces, urine

Adverse effects

·        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, indomethacin, and rifamycin

·        Losartan is converted to an active metabolite by cytochrome P450-3A4 and 2C9 (fluconazole). Drugs that inhibit 3A4 (ketoconazole, fluconazole, diltiazem) may decrease the antihypertensive effects of losartan

Nursing considerations

Assessment

·        History: Hypersensitivity to losartan, pregnancy, lactation, hepatic or renal dysfunction, hypovolemia

·        Physical: Skin lesions, turgor; T; reflexes, affect; BP; R, respiratory auscultation; LFTs, renal function tests

Interventions

·        Administer without regard to meals.

·        WARNING: 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.

·        WARNING: 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 BP secondary to reduction in fluid volume—excessive perspiration, dehydration, vomiting, diarrhea—excessive hypotension can occur.

Teaching points

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

·        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.

·        You may experience these side effects: Dizziness (avoid driving a car or performing hazardous tasks); headache (request medications); nausea, vomiting, diarrhea (proper nutrition is important, consult a 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.