Nurses Compass
Drug Guide
Hydrochlorothiazide; Irbesartan
Classification
Therapeutic: Antihypertensive, Diuretic
Pharmacological: Angiotensin II Receptor Blocker (Irbesartan) combined with Thiazide Diuretic (Hydrochlorothiazide)
FDA Approved Indications
- Treatment of hypertension to reduce blood pressure
Mechanism of Action
Irbesartan blocks angiotensin II receptors, leading to vasodilation and decreased blood pressure. Hydrochlorothiazide inhibits sodium reabsorption in the distal tubules of the kidney, promoting diuresis and reducing blood volume, which lowers blood pressure.
Dosage and Administration
Adult: Typically 150 mg of irbesartan with 12.5 mg of hydrochlorothiazide once daily; dosage may be adjusted based on response.
Pediatric: Not approved for pediatric use.
Geriatric: Adjust dose based on renal function; start at lower end of dosing range.
Renal Impairment: Use with caution; dose adjustment may be necessary.
Hepatic Impairment: Use with caution; no specific dose adjustment approved.
Pharmacokinetics
Absorption: Irbesartan is well absorbed; hydrochlorothiazide absorption is incomplete but consistent.
Distribution: Irbesartan is approximately 95% protein-bound; hydrochlorothiazide is moderately protein-bound.
Metabolism: Irbesartan undergoes minimal metabolism; hydrochlorothiazide is not extensively metabolized.
Excretion: Irbesartan excreted primarily via feces and urine; hydrochlorothiazide mainly excreted unchanged in urine.
Half Life: Irbesartan: approximately 11-15 hours; hydrochlorothiazide: about 6-15 hours.
Contraindications
- Hypersensitivity to irbesartan, hydrochlorothiazide, or sulfonamides.
- Anuria.
Precautions
- Pregnancy (category D), especially after the first trimester.
- History of angioedema related to previous ACE inhibitor or ARB therapy.
- Electrolyte disturbances, renal impairment, hepatic impairment.
Adverse Reactions - Common
- Dizziness (common)
- Hypotension (common)
- Electrolyte imbalance (e.g., hypokalemia, hyponatremia) (common)
Adverse Reactions - Serious
- Angioedema (rare)
- Renal failure (rare)
- Hypersensitivity reactions (rare)
Drug-Drug Interactions
- Other antihypertensives, especially diuretics and ACE inhibitors.
- Lithium (increased risk of toxicity).
- NSAIDs (may reduce antihypertensive effect).
Drug-Food Interactions
- Excessive potassium intake (risk of hyperkalemia).
Drug-Herb Interactions
N/ANursing Implications
Assessment: Monitor blood pressure, renal function, and electrolyte levels regularly.
Diagnoses:
- Risk for electrolyte imbalance
- Ineffective tissue perfusion related to hypotension
Implementation: Administer with food to reduce gastrointestinal upset; monitor for signs of hypotension, electrolyte disturbances.
Evaluation: Assess blood pressure and laboratory values periodically to evaluate effectiveness and safety.
Patient/Family Teaching
- Take medication exactly as prescribed.
- Report signs of allergic reactions, angioedema, or severe dizziness.
- Be cautious about potassium intake.
- Avoid pregnancy and use reliable contraception.
Special Considerations
Black Box Warnings:
- Pregnancy category D; fetal toxicity.
Genetic Factors: None specified.
Lab Test Interference: Can cause alterations in serum electrolyte and renal function tests.
Overdose Management
Signs/Symptoms: Severe hypotension, electrolyte disturbances, dehydration.
Treatment: Stop medication, provide supportive care, rehydrate as needed, monitor electrolytes and renal function.
Storage and Handling
Storage: Store at room temperature, 15-30°C.
Stability: Stable under recommended storage conditions.