Drug Guide
Losartan Potassium
Classification
Therapeutic: Antihypertensive, Angiotensin II Receptor Blocker (ARB)
Pharmacological: Competitive AT1 receptor antagonist
FDA Approved Indications
- Hypertension
- Reduce the risk of stroke in patients with hypertension and left ventricular hypertrophy
- Diabetic nephropathy with proteinuria in patients with type 2 diabetes
Mechanism of Action
Losartan blocks the binding of angiotensin II to the AT1 receptor, resulting in vasodilation, decreased aldosterone secretion, and reduction in blood pressure; it also reduces glomerular hypertension in diabetic nephropathy.
Dosage and Administration
Adult: Typically 50 mg once daily, titrated up to 100 mg once daily based on response and tolerability.
Pediatric: Not recommended for children under 6 years. Dosing for older children depends on weight and clinical condition.
Geriatric: Start at lower dose due to increased sensitivity and risk of hypotension.
Renal Impairment: Adjust dose in patients with renal impairment; may be used cautiously.
Hepatic Impairment: Use with caution; no specific dose adjustment required.
Pharmacokinetics
Absorption: Well absorbed from GI tract, with about 33% bioavailability.
Distribution: Widely distributed, crosses placenta.
Metabolism: Metabolized in the liver to an active metabolite, EXP3174.
Excretion: Excreted primarily via urine and feces.
Half Life: Approximately 2 hours for losartan; active metabolite has a half-life of about 6-9 hours.
Contraindications
- Pregnancy (especially 2nd and 3rd trimesters)
- History of hypersensitivity to losartan or other ARBs
Precautions
- Pregnancy category D, caution in patients with bilateral renal artery stenosis, hepatic impairment, volume-depleted states
Adverse Reactions - Common
- Dizziness (Common)
- Hyperkalemia (Common)
- Arthralgia (Less common)
Adverse Reactions - Serious
- Angioedema (Rare)
- Hypotension (Rare)
- Elevated serum creatinine or blood urea nitrogen (BUN) (Rare)
Drug-Drug Interactions
- Other antihypertensives, potassium-sparing diuretics, lithium, NSAIDs
Drug-Food Interactions
- Avoid potassium-rich supplements or salt substitutes containing potassium
Drug-Herb Interactions
- Potential interactions with herbal supplements affecting blood pressure or potassium levels
Nursing Implications
Assessment: Monitor blood pressure, serum potassium, renal function (BUN, serum creatinine) regularly.
Diagnoses:
- Risk for electrolyte imbalance
- Risk for hypotension
Implementation: Administer as prescribed, monitor patient response, educate about symptom reporting.
Evaluation: Assess blood pressure for effectiveness; monitor for signs of hyperkalemia or renal impairment.
Patient/Family Teaching
- Take medication exactly as prescribed.
- Do not discontinue without consulting healthcare provider.
- Avoid potassium supplements or salt substitutes unless directed.
- Report symptoms like swelling, dizziness, or irregular heartbeat.
Special Considerations
Black Box Warnings:
- Pregnancy-associated morbidity and fetal death—discontinue as soon as pregnancy is detected.
Genetic Factors: Genetic polymorphisms may influence response to therapy.
Lab Test Interference: May increase serum potassium and serum creatinine.
Overdose Management
Signs/Symptoms: Severe hypotension, tachycardia or bradycardia, electrolyte disturbances.
Treatment: Supportive care, monitor vital signs, correct electrolyte imbalances, administer vasopressors if needed.
Storage and Handling
Storage: Store at room temperature, away from moisture and light.
Stability: Stable for 2-3 years when stored properly.