Hyzaar (Losartan Potassium, Hydrochlorothiazide)

Hyzaar combines an angiotensin II receptor blocker with a thiazide diuretic to manage high blood pressure.

• Essential hypertension: lowers systolic and diastolic pressure in adult patients.
• Hypertension with fluid retention: provides diuretic action to reduce plasma volume.
• Hypertension requiring combination therapy: offers dual mechanisms to improve blood pressure control.

• Losartan potassium selectively blocks AT1 angiotensin II receptors, preventing vasoconstriction and aldosterone release, while hydrochlorothiazide inhibits NaCl reabsorption in the distal convoluted tubule, promoting diuresis and reducing plasma volume. The combined effect results in decreased peripheral resistance and lower blood pressure.

Common Side Effects

• Dizziness: feeling light‑headed, especially after standing.
• Headache: mild to moderate intensity.
• Fatigue: general tiredness or lack of energy.
• Increased urination: due to the diuretic component.
• Muscle cramps: occasional leg or calf cramps.
• Nausea: mild stomach upset.

Serious or Rare Side Effects

• Severe dehydration: marked fluid loss requiring medical attention.
• Hyperkalemia: elevated potassium levels that can affect heart rhythm.
• Acute kidney injury: sudden decline in renal function.
• Angioedema: swelling of face, lips, tongue, or throat.
• Severe hypotension: dangerously low blood pressure.
• Allergic reactions: rash, itching, or anaphylaxis.

Before initiating Hyzaar, consider the following precautions.

• Monitor blood pressure: ensure adequate control and avoid excessive lowering.
• Check electrolytes: especially potassium and sodium levels.
• Avoid in pregnancy: drug is classified as Category D and may harm the fetus.
• Use caution in renal impairment: dose adjustment may be required.
• Do not discontinue abruptly: taper under medical supervision.
• Store at room temperature: keep in the original container, protect from moisture and direct sunlight.

Hyzaar may interact with several medicines; review the following.

Major Interactions (Avoid)

• Aliskiren (in diabetes): increased risk of renal dysfunction.
• Potassium‑sparing diuretics: risk of hyperkalemia.
• NSAIDs: may reduce antihypertensive effect.
• Lithium: increased lithium toxicity.
• ACE inhibitors or other ARBs: additive potassium elevation.

Moderate Interactions (Monitor Closely)

• Other antihypertensives: additive blood pressure lowering.
• Loop diuretics: monitor electrolyte balance.
• Antidiabetic agents: possible enhanced hypoglycemia.
• CYP2C9 inhibitors (e.g., fluconazole): may increase losartan levels.
• Antacids containing aluminum or magnesium: may affect absorption.