Losartan Potassium and Hydrochlorothiazide Tablets (Hyzaar) is a combined antihypertensive drug composed of losartan potassium (an angiotensin II receptor blocker, ARB) and hydrochlorothiazide (a diuretic). It is indicated for the treatment of hypertension and for reducing the risk of stroke in patients with hypertension and left ventricular hypertrophy.

How to Administer Losartan Potassium and Hydrochlorothiazide Tablets (Hyzaar)

For Hypertension Treatment

Initial dose: The recommended starting dose is 50/12.5 mg (50 mg losartan potassium / 12.5 mg hydrochlorothiazide), taken once daily.

If blood pressure control is inadequate, the dose can be gradually increased to the maximum dose of 100/25 mg once daily after 3 weeks.

Switching from Monotherapy

If a patient previously using 50 mg losartan potassium monotherapy fails to achieve target blood pressure, they can switch to Hyzaar 50/12.5 mg. If efficacy remains insufficient, the dose can be adjusted to 100/25 mg or two tablets of 50/12.5 mg taken together.

If a patient develops hypokalemia while using 25 mg hydrochlorothiazide monotherapy, they can switch to Hyzaar 50/12.5 mg to reduce the risk of electrolyte imbalance.

For Hypertension Complicated with Left Ventricular Hypertrophy

For patients with inadequate blood pressure control on monotherapy, it is recommended to start with Hyzaar 50/12.5 mg, and gradually adjust the dose to 100/12.5 mg or 100/25 mg. Additional antihypertensive drugs may be combined if necessary.

It should be noted that Black patients may not achieve the same stroke risk reduction benefit.

Administration of Losartan Potassium and Hydrochlorothiazide Tablets (Hyzaar) in Special Populations

Pregnant Women

Contraindication: Use during the second and third trimesters of pregnancy can cause fetal renal damage, skull hypoplasia, or even fetal death. The drug must be discontinued immediately upon confirmation of pregnancy.

Risk warning: Hydrochlorothiazide can cross the placenta, potentially causing fetal jaundice or thrombocytopenia; its use should be avoided during pregnancy.

Patients with Hepatic or Renal Impairment

Hepatic Impairment

Initial treatment with this combination tablet is not recommended, as a 25 mg starting dose (for losartan) is not available in this formulation. Dose adjustment must be performed with caution in patients with severe liver disease.

Renal Impairment

For patients with mild to moderate renal impairment, regular monitoring of renal function and serum potassium levels is required to avoid acute renal failure induced by volume depletion.

The safety of this drug in patients with a creatinine clearance < 30 mL/min has not been established, and its use is contraindicated in such cases.

Elderly Patients

The efficacy of the drug in elderly patients (≥ 65 years old) is comparable to that in younger patients, but the incidence of adverse reactions may be slightly higher. Enhanced monitoring of blood pressure and electrolyte levels is required.

Pediatric Patients and Lactating Women

Pediatric patients: The efficacy of this drug in pediatric patients has not been established, and its use is not recommended.

Lactating women: It is unclear whether losartan potassium is excreted into human milk, but hydrochlorothiazide can pass into breast milk. A careful balance of benefits and risks is recommended, with consideration given to either discontinuing the drug or ceasing breastfeeding.

Precautions and Potential Risks of Losartan Potassium and Hydrochlorothiazide Tablets (Hyzaar)

Effects on Electrolytes and Metabolism

Hydrochlorothiazide may cause hypokalemia, hyponatremia, hypomagnesemia, and hyperuricemia, while losartan potassium may induce hyperkalemia. Regular monitoring of electrolyte levels is required.

Drug Interactions

Potassium-elevating drugs: Concomitant use with potassium supplements or potassium-sparing diuretics may lead to hyperkalemia.

NSAIDs: Nonsteroidal anti-inflammatory drugs may reduce the antihypertensive effect and increase the risk of renal injury; concurrent use should be avoided.

Lithium preparations: Hydrochlorothiazide can increase serum lithium concentrations; close monitoring of lithium levels is required if combined use is necessary.

Other Warnings

Allergic reactions: Patients allergic to sulfonamide drugs may experience cross-allergic reactions (hydrochlorothiazide is a sulfonamide derivative).

Acute glaucoma: A rare but severe sulfonamide-related reaction, manifested as a sudden decrease in visual acuity. Immediate drug discontinuation and medical attention are required if this occurs.