Treatment of essential hypertension (high blood pressure) when monotherapy is insufficient or for patients requiring combination therapy; Reduction of stroke risk in patients with hypertension and left ventricular hypertrophy (LVH); May help manage associated fluid retention/edema. Not first-line for all patients—often used when blood pressure is not controlled by single agents.

Adults: Usually 1 tablet (50 mg/12.5 mg) once daily; may increase to higher strengths (e.g., 100 mg/12.5 mg or 100 mg/25 mg equivalents) if needed after 3–6 weeks based on response. Max typical: 100 mg losartan/25 mg hydrochlorothiazide daily.
Start lower in volume-depleted patients (e.g., on diuretics) to avoid hypotension.
No routine pediatric use for this strength; adjust in renal impairment (monitor closely if CrCl <30 mL/min—may need alternatives); avoid in severe hepatic impairment. Regular BP/electrolyte monitoring required.

Common (>1%): Dizziness/lightheadedness (especially initial doses or standing), headache, fatigue/tiredness, nausea, diarrhea, abdominal pain, back pain, cough (less common than with ACE inhibitors), upper respiratory symptoms (cold/flu-like), muscle cramps/weakness (from diuretic effect).
Serious (rare, seek immediate care): Severe hypotension, hyperkalemia (high potassium), acute kidney injury, electrolyte imbalances (low sodium/potassium/magnesium), angioedema (swelling of face/lips/tongue—rare with ARBs), severe allergic reactions, gout flares (from hyperuricemia), photosensitivity.

Monitor electrolytes (especially potassium, sodium) and renal function regularly—risk of hyperkalemia or dehydration.
Avoid in pregnancy (can cause fetal harm/injury/death—discontinue immediately if pregnant); contraindicated in breastfeeding (hydrochlorothiazide passes into milk).
Use caution in bilateral renal artery stenosis, volume/salt depletion, heart failure, diabetes (may affect blood sugar), gout history, or SLE (lupus—may worsen).
May cause orthostatic hypotension—rise slowly from sitting/lying.
Frequent urination is expected (diuretic effect)—stay hydrated but monitor for dehydration signs (dry mouth, thirst, weakness).
Not for acute hypertensive crisis.

Pregnancy: Contraindicated (FDA former Category D); can cause fetal renal damage, oligohydramnios, skull hypoplasia, or death—avoid entirely; use effective contraception.
Lactation: Not recommended—hydrochlorothiazide excreted in breast milk (risk of infant jaundice, thrombocytopenia); losartan data limited—consult provider/alternatives preferred.

Potassium-sparing diuretics (e.g., spironolactone), potassium supplements/salt substitutes: Risk of hyperkalemia—monitor closely.
Lithium: Increased levels/toxicity—avoid or monitor.
NSAIDs (e.g., ibuprofen): Reduced antihypertensive effect + renal risk.
Other antihypertensives: Additive hypotension.
Alcohol/CNS depressants: Enhanced dizziness.
Cholestyramine/colestipol: Reduced hydrochlorothiazide absorption.

Known hypersensitivity to losartan, hydrochlorothiazide, sulfonamides (cross-reactivity), or any component.
Anuria (no urine output) or severe renal impairment without dialysis.
Pregnancy (second/third trimester especially).
Concomitant aliskiren in diabetic patients (increased renal risk).