Home Drug Guide Hydrochlorothiazide; Losartan Potassium

Drug Guide

Generic Name

Hydrochlorothiazide; Losartan Potassium

Brand Names Hyzaar, Losartan Potassium and Hydrochlorothiazide

Classification

Therapeutic: Antihypertensive

Pharmacological: Angiotensin II Receptor Blocker (Losartan) with Diuretic (Hydrochlorothiazide)

FDA Approved Indications

Hypertension
Reduced risk of stroke in patients with hypertension and left ventricular hypertrophy

Mechanism of Action

Losartan blocks the angiotensin II receptors, preventing vasoconstriction and aldosterone release, thereby lowering blood pressure. Hydrochlorothiazide increases excretion of sodium and water, decreasing blood volume and pressure.

Dosage and Administration

Adult: Typically, 50 mg once daily, may be adjusted; max 100 mg of losartan and 25 mg hydrochlorothiazide daily.

Pediatric: Not approved for pediatric use.

Geriatric: Start at lower doses due to increased sensitivity; monitor renal function and electrolytes closely.

Renal Impairment: Adjust dose; avoid in severe renal impairment (creatinine clearance <30 mL/min).

Hepatic Impairment: Use with caution; no specific dose adjustment available.

Pharmacokinetics

Absorption: Rapidly absorbed; peak plasma levels in 2 hours.

Distribution: Losartan is approximately 99% bound to plasma proteins; hydrochlorothiazide is about 40%.

Metabolism: Losartan undergoes hepatic metabolism; hydrochlorothiazide is not metabolized.

Excretion: Primarily via urine; Losartan's active metabolite excreted in bile and urine.

Half Life: Losartan: approximately 2 hours; active metabolite: 6-9 hours; Hydrochlorothiazide: 6-15 hours.

Contraindications

Hypersensitivity to sulfamides, losartan, or hydrochlorothiazide
Pregnancy (second and third trimesters)

Precautions

Renal impairment, sodium or volume depletion, liver impairment, history of angioedema. May cause hyperkalemia, dehydration, hypotension. Use with caution in patients on other antihypertensives or diuretics.

Adverse Reactions - Common

Dizziness (Common)
Hyperkalemia (Less common)
Hypotension (Common)
Dizziness or lightheadedness upon standing (Common)

Adverse Reactions - Serious

Angioedema (Rare)
Severe hypotension or renal failure (Rare)
Electrolyte disturbances (hypokalemia, hyponatremia) (Less common)

Drug-Drug Interactions

Potassium supplements, other antihypertensives, lithium, NSAIDs

Drug-Food Interactions

N/A

Drug-Herb Interactions

N/A

Nursing Implications

Assessment: Monitor blood pressure, renal function, serum electrolytes, signs of edema.

Diagnoses:

Risk for decreased cardiac output related to hypotension
Risk for electrolyte imbalance

Implementation: Administer as prescribed, monitor vitals and labs regularly, educate patient on symptoms of imbalance.

Evaluation: Assess blood pressure response, renal function, and electrolyte levels to determine effectiveness and safety.

Patient/Family Teaching

Take medication exactly as prescribed.
Report signs of hyperkalemia (muscular weakness, irregular heartbeat), angioedema, or severe dizziness.
Avoid excessive potassium intake unless directed.
Monitor blood pressure regularly at home.

Special Considerations

Black Box Warnings:

Pregnancy: Use during second and third trimesters can cause injury or death to the fetus.

Genetic Factors: Genetic variations may affect response, such as CYP2C9 polymorphisms affecting losartan metabolism.

Lab Test Interference: Potential interference with serum potassium, renal function tests.

Overdose Management

Signs/Symptoms: Severe hypotension, dizziness, dehydration, electrolyte imbalance.

Treatment: Stop medication, support vital signs, correct electrolyte imbalances, administer activated charcoal if ingestion was recent.

Storage and Handling

Storage: Store at room temperature away from light and moisture.

Stability: Stable under recommended storage conditions.