What are the guidelines for laboratory tests and initiating Losartan (Angiotensin II receptor antagonist)?

From the Guidelines

When initiating losartan, baseline labs should be obtained including serum creatinine, potassium, and estimated glomerular filtration rate (eGFR), and these labs should be checked again 2 to 4 weeks after initiating therapy, as recommended by the 2017 American College of Cardiology/American Heart Association hypertension guideline 1.

Key Considerations for Losartan Initiation

• The typical starting dose for hypertension is 50 mg once daily, which can be increased to 100 mg daily if needed for blood pressure control.
• For patients with volume depletion, those on diuretics, or those with renal impairment (eGFR <30 mL/min), start with a lower dose of 25 mg daily.
• Losartan is contraindicated in pregnancy and should not be used in patients with bilateral renal artery stenosis.
• Regular monitoring of potassium levels is important as losartan can cause hyperkalemia, especially in patients with renal impairment or those taking potassium supplements or potassium-sparing medications.

Monitoring and Dose Adjustment

• If serum creatinine increases by >30% or potassium exceeds 5.5 mEq/L, consider dose reduction or discontinuation.
• Losartan works by blocking angiotensin II receptors, leading to vasodilation and decreased aldosterone secretion, which helps lower blood pressure and provides renal and cardiovascular protection.

Additional Guidance

• The 2017 American College of Cardiology/American Heart Association hypertension guideline recommends that clinicians should consider initiation of pharmacologic therapy for stage 2 hypertension with 2 antihypertensive agents from different classes 1.
• The European Society of Hypertension and the European Society of Cardiology also provide guidance on the management of arterial hypertension, including the use of losartan in elderly patients 1.

From the FDA Drug Label

The usual starting dose of losartan is 50 mg once daily. A starting dose of 25 mg is recommended for patients with possible intravascular depletion (e.g., on diuretic therapy). Dosage should be adjusted according to blood pressure response.

The guidelines for initiating losartan are to start with a dose of 50 mg once daily, with a recommended starting dose of 25 mg for patients with possible intravascular depletion. The dosage should be adjusted based on blood pressure response 2.

• Key considerations for initiating losartan include:
  • Starting dose: 50 mg once daily
  • Adjusted starting dose for patients with possible intravascular depletion: 25 mg
  • Dosage adjustment: based on blood pressure response
• Laboratory monitoring is not explicitly mentioned in the provided drug labels as a guideline for initiating losartan 2 2.

From the Research

Guidelines for Labs and Initiating Losartan

• Losartan potassium is an orally active, nonpeptide angiotensin II (AII) receptor antagonist, and its use in patients with hypertension has been studied extensively 3, 4.
• The drug is effective as a once-daily antihypertensive agent, with similar efficacy to enalapril, atenolol, and felodipine extended release in patients with mild to moderate hypertension 3, 4.
• Losartan potassium is well tolerated, with dizziness being reported as the only drug-related adverse effect, and first-dose hypotension is uncommon 3, 4.
• The combination of losartan potassium with hydrochlorothiazide reduces blood pressure further than either drug given separately, and is effective in patients with severe hypertension 3, 4.

Laboratory Tests and Monitoring

• Renal function should be monitored in patients taking losartan, particularly in those with pre-existing renal insufficiency 5, 6.
• Losartan has been shown to retard the progression of advanced renal insufficiency, and may be beneficial in patients with chronic renal disease 5.
• Laboratory tests should include measurements of serum creatinine, potassium, and uric acid levels, as well as urine protein and sodium excretion 6.
• Losartan may increase uric acid secretion and lower plasma uric acid levels, which may be of benefit when combined with a thiazide diuretic, but may also lead to uric acid stone formation and nephropathy 4, 6.

Special Considerations

• Losartan may be used in patients with renal insufficiency, but dosage adjustment may be necessary in patients with severe renal impairment 7.
• The use of losartan in patients with hepatic disease requires further investigation, and patients with a history of ACE inhibitor-related cough should be monitored closely 4.
• Losartan may be beneficial in patients with essential hypertension who are intolerant of ACE inhibitors, but long-term tolerability studies and data on its effects beyond simple blood pressure control are needed to fully assess its potential 3, 4.