LOSARTAN POTASSIUM

LOSARTAN POTASSIUM
(lo-sar'tan)
Cozaar
Classifications: angiotensin ii receptor antagonist; antihypertensive;
Therapeutic: antihypertensive
; angiotensin ii receptor antagonist
Pregnancy Category: C first trimester; D second and third trimester

Availability

25 mg, 50 mg tablet

Action

Angiotensin II receptor (type AT1) antagonist acts as a potent vasoconstrictor and primary vasoactive hormone of the renin–angiotensin–aldosterone system. Selectively blocks the binding of angiotensin II to the AT1 receptors found in many tissues (e.g., vascular smooth muscle, adrenal glands). Antihypertensive effect results from blocking vasoconstricting and aldosterone-secreting effects of angiotensin II.

Therapeutic Effect

Antihypertensive effect is due to vasodilation and inhibition of aldosterone effects on sodium and water retention.

Uses

Hypertension.

Contraindications

Hypersensitivity to losartan, children <6 y or children with Clcr <30 mL/min/1.73 m2; pregnancy [category C (first trimester), category D (second and third trimesters)], lactation.

Cautious Use

Patients on diuretics, heart failure; hyperkalemia; hypovolemia; renal or hepatic impairment.

Route & Dosage

Hypertension
Adult: PO 25–50 mg in 1–2 divided doses (max: 100 mg/d); start with 25 mg/d if volume depleted (i.e., on diuretics)

Administration

Oral
  • Note: Starting dose is reduced 50% in patients with possible volume depletion or a history of liver disease.

Adverse Effects (≥1%)

CNS: Dizziness, insomnia, headache. GI: Diarrhea, dyspepsia. Musculoskeletal: Muscle cramps, myalgia, back or leg pain. Respiratory: Nasal congestion, cough, upper respiratory infection, sinusitis.

Interactions

Drug: Phenobarbital decreases serum levels of losartan and its metabolite.

Pharmacokinetics

Absorption: Rapidly absorbed from GI tract; approximately 25–33% reaches systemic circulation. Peak: 6 h. Duration: 24 h. Distribution: Highly bound to plasma proteins; does not appear to cross blood–brain barrier. Metabolism: Extensively metabolized in liver by cytochrome P450 enzymes to an active metabolite. Elimination: 35% in urine, 60% in feces. Half-Life: Losartan 1.5–2 h; metabolite 6–9 h.

Nursing Implications

Assessment & Drug Effects

  • Monitor BP at drug trough (prior to a scheduled dose).
  • Monitor drug effectiveness, especially in African-Americans when losartan is used as monotherapy.
  • Inadequate response may be improved by splitting the daily dose into twice-daily dose.
  • Lab tests: Monitor CBC, electrolytes, liver & kidney function with long-term therapy.

Patient & Family Education

  • Notify physician of symptoms of hypotension (e.g., dizziness, fainting).
  • Notify physician immediately of pregnancy.

Common adverse effects in italic, life-threatening effects underlined; generic names in bold; classifications in SMALL CAPS; Canadian drug name; Prototype drug

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