💊 Losartan (Losartan Potassium And Hydrochlorothiazide)

✅ What it is used for

• Treatment of hypertension (high blood pressure).
• Reducing the risk of stroke in patients with hypertension and left ventricular hypertrophy, although there is evidence that this benefit does not apply to Black patients.
• This combination is not generally for initial therapy of hypertension, except when blood pressure is severe enough that prompt control outweighs the risk of starting combination therapy.

🧪 Active ingredient

Losartan blocks the AT1 angiotensin II receptor, preventing vasoconstriction and aldosterone secretion. Hydrochlorothiazide is a thiazide diuretic that increases renal excretion of sodium and chloride, reducing plasma volume.

🌿 Benefits

• Lowers blood pressure.
• Reduces stroke risk in hypertensive patients with left ventricular hypertrophy (except as noted regarding Black patients).
• The losartan component tends to reverse the potassium loss associated with thiazide diuretics.

📝 How to use

• Taken by mouth.
• The dose must be individualized and set by your doctor or pharmacist; do not change it on your own.
• Combination therapy is usually started only after the desired effect was not achieved with one of the components alone.
• The doctor evaluates the response after about 3 weeks and may adjust the dose according to blood pressure.

💊 Dosage forms

• Film-coated tablets 50 mg/12.5 mg.
• Film-coated tablets 100 mg/12.5 mg.
• Film-coated tablets 100 mg/25 mg.

🔄 Drug interactions

• Aliskiren: must not be co-administered in patients with diabetes.
• Rifampin and phenobarbital: may lower levels of losartan and its active metabolite.
• Fluconazole: decreased the active metabolite and increased losartan exposure.
• Cimetidine: modestly increased losartan exposure.
• Erythromycin: increased losartan exposure.
• No significant interaction was found with digoxin or warfarin.
• Tell your doctor or pharmacist about all medicines you take.

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👨‍⚕️ For healthcare professionals

Mechanism of action

Losartan and its active metabolite (10 to 40 times more potent by weight) block angiotensin II binding at the AT1 receptor without inhibiting ACE, blocking vasoconstriction and aldosterone secretion. Hydrochlorothiazide, a thiazide diuretic, increases sodium and chloride excretion, reduces plasma volume, and raises plasma renin activity, aldosterone secretion and urinary potassium loss; coadministration of an angiotensin II antagonist tends to reverse this.

Labeled dosing

Dosing must be individualized. Usual losartan starting dose is 50 mg once daily (25 mg for intravascular volume depletion or hepatic impairment history), total daily doses 25 to 100 mg. Hydrochlorothiazide is effective at 12.5 to 50 mg once daily and is given at 12.5 to 25 mg in the combination. The usual dose is one 50 mg/12.5 mg tablet once daily; if uncontrolled after about 3 weeks, increase to two 50 mg/12.5 mg tablets or one 100 mg/25 mg tablet once daily.

• Not for initial therapy except in severe hypertension.
• Begin combination therapy after failure of monotherapy to minimize dose-independent side effects.
• Patients on hydrochlorothiazide 25 mg with inadequate control or hypokalemia may switch to 50 mg/12.5 mg, reducing the thiazide dose without losing the expected antihypertensive response.
• The label includes cautions for volume depletion and hepatic impairment.

🎓 Key points for students

• Class: angiotensin II receptor (AT1) blocker plus thiazide diuretic.
• Losartan does not inhibit ACE or affect bradykinin degradation.
• Hydrochlorothiazide causes potassium loss, which losartan tends to counteract.
• Boxed warning for fetal toxicity.
• Contraindicated in anuria, sulfonamide hypersensitivity, and with aliskiren in diabetes.
• Plasma half-life of hydrochlorothiazide ranges from 5.6 to 14.8 hours.