Usage
- Atenolol + Hydrochlorothiazide is primarily prescribed for the management of hypertension (high blood pressure). This combination therapy is particularly useful when monotherapy with either drug fails to achieve adequate blood pressure control.
- Pharmacological Classification: Atenolol is a cardioselective beta-blocker and Hydrochlorothiazide is a thiazide diuretic. The combination is thus classified as an antihypertensive.
- Mechanism of Action: Atenolol works by blocking beta-1 adrenergic receptors in the heart, reducing heart rate and cardiac output. Hydrochlorothiazide increases the excretion of sodium and water by the kidneys, leading to a decrease in blood volume. The combined effect of these two mechanisms lowers blood pressure.
Alternate Names
- Atenolol + Hydrochlorothiazide is also referred to as Atenolol/Hydrochlorothiazide combination or Atenolol HCTZ.
- Brand Names: Tenoretic. Other brand names may exist regionally.
How It Works
- Pharmacodynamics: Atenolol reduces heart rate, myocardial contractility, and cardiac output, while Hydrochlorothiazide decreases peripheral vascular resistance.
- Pharmacokinetics:
- Atenolol is partially absorbed orally, with peak plasma concentrations reached in 2-4 hours. It has relatively low protein binding and undergoes minimal hepatic metabolism. Elimination primarily occurs through renal excretion.
- Hydrochlorothiazide is well absorbed orally and reaches peak plasma levels in 1-2 hours. It has moderate protein binding and is excreted unchanged by the kidneys.
- Mode of Action:
- Atenolol competitively blocks beta-1 adrenergic receptors, reducing the effects of sympathetic nervous system stimulation on the heart. It primarily acts on cardiac tissue.
- Hydrochlorothiazide inhibits sodium reabsorption in the distal convoluted tubule of the nephron, leading to increased sodium and water excretion.
- Elimination Pathways: Both atenolol and hydrochlorothiazide are primarily excreted renally.
Dosage
Standard Dosage
Adults:
- Initial: Atenolol 50 mg + Hydrochlorothiazide 12.5 mg orally once daily.
- Maintenance: May increase to Atenolol 100 mg + Hydrochlorothiazide 25 mg orally once daily. Hydrochlorothiazide doses >50 mg are not recommended. Atenolol doses greater than 100 mg are unlikely to have additional benefit.
- Timing: Administer once daily, preferably in the morning.
Children:
- Not recommended for use in patients under 18 years of age.
Special Cases:
- Elderly Patients: Initial dose of Atenolol may be reduced to 25 mg once daily, with careful monitoring and titration.
- Patients with Renal Impairment:
- CrCl 15-35 mL/min: Atenolol maximum dose 50 mg daily.
- CrCl <15 mL/min: Atenolol maximum dose 25 mg daily or 50 mg every other day.
- Hydrochlorothiazide is not recommended with CrCl less than 30ml/min.
- Patients with Hepatic Dysfunction: Use with caution in patients with hepatic impairment. Lower initial doses of Atenolol are recommended.
- Patients with Comorbid Conditions: Patients with asthma, COPD, or diabetes should be monitored carefully. Atenolol may mask the symptoms of hypoglycemia.
Clinical Use Cases
- This specific combination (atenolol + hydrochlorothiazide) doesn’t have specific dosage guidelines for intubation, surgical procedures, mechanical ventilation, ICU use, or emergency situations. In these cases, the individual components might be used with different dosing considerations.
Dosage Adjustments
- Dose adjustments should be based on individual patient response and tolerability, as well as renal and hepatic function.
Side Effects
Common Side Effects:
- Dizziness, lightheadedness, fatigue, bradycardia, hypotension, cold extremities.
- Electrolyte imbalances (hypokalemia, hyponatremia, hypomagnesemia).
Rare but Serious Side Effects:
- Bronchospasm, heart failure exacerbation, heart block.
Long-Term Effects:
- Electrolyte imbalances, metabolic disturbances.
Adverse Drug Reactions (ADR):
- Angioedema, Stevens-Johnson syndrome, toxic epidermal necrolysis (rare).
Contraindications
- Second or third-degree heart block (without a pacemaker), sinus bradycardia, cardiogenic shock, uncompensated heart failure.
- Severe bronchospastic disease.
- Hypersensitivity to either atenolol or hydrochlorothiazide or sulfonamide-derived medications.
- Anuria.
Drug Interactions
- Other antihypertensives (additive hypotensive effects).
- Calcium channel blockers (may potentiate bradycardia or heart block).
- Digoxin (may increase risk of bradycardia).
- Insulin or oral hypoglycemic agents (atenolol may mask hypoglycemia).
- Nonsteroidal anti-inflammatory drugs (NSAIDs) (may reduce the antihypertensive effect).
Pregnancy and Breastfeeding
- Pregnancy Safety Category: Previously classified as Category D. Not recommended during pregnancy due to potential risks of fetal growth restriction and neonatal bradycardia and hypoglycemia.
- Breastfeeding: Atenolol is excreted in breast milk and may cause bradycardia and hypoglycemia in infants. Avoid use during breastfeeding.
Drug Profile Summary
- Mechanism of Action: Atenolol: Beta-1 adrenergic blocker, Hydrochlorothiazide: Thiazide diuretic.
- Side Effects: Dizziness, fatigue, bradycardia, hypotension, electrolyte imbalances.
- Contraindications: Heart block, bradycardia, cardiogenic shock, uncompensated heart failure, hypersensitivity.
- Drug Interactions: Other antihypertensives, calcium channel blockers, digoxin, insulin/oral hypoglycemics, NSAIDs.
- Pregnancy & Breastfeeding: Not recommended.
- Dosage: Adults: Initial: Atenolol 50 mg + HCTZ 12.5 mg once daily; may increase to Atenolol 100 mg + HCTZ 25 mg once daily.
- Monitoring Parameters: Blood pressure, heart rate, electrolytes (potassium, sodium, magnesium), renal function, blood glucose.
Popular Combinations
- Atenolol and Hydrochlorothiazide is itself a popular combination. Sometimes, other antihypertensives may be added if blood pressure control is inadequate.
Precautions
- Monitor blood pressure and heart rate regularly.
- Assess renal and hepatic function before and during treatment.
- Monitor for electrolyte imbalances, particularly in elderly patients and those with renal impairment.
- Monitor diabetic patients for masked hypoglycemia.
- Advise patients not to abruptly discontinue therapy to avoid rebound hypertension or angina.
- Use cautiously in patients with asthma/COPD.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Atenolol + Hydrochlorothiazide?
A: Initial dose is Atenolol 50 mg and Hydrochlorothiazide 12.5 mg once a day. This can be increased to Atenolol 100 mg and Hydrochlorothiazide 25 mg once a day if needed.
Q2: Can this combination be used in patients with asthma?
A: Atenolol, as a beta-blocker, can exacerbate bronchospasm. Use with extreme caution in patients with asthma or other respiratory conditions. A cardioselective beta blocker like atenolol is preferred over non-selective beta-blockers if a beta blocker needs to be used in a patient with asthma.
Q3: What are the common side effects to watch for?
A: Dizziness, lightheadedness, fatigue, bradycardia, and hypotension are common side effects. Electrolyte imbalances like hypokalemia can also occur.
Q4: Are there any specific monitoring parameters for this combination?
A: Monitor blood pressure, heart rate, and electrolytes. Monitor renal function and blood glucose, particularly in patients with pre-existing diabetes.
Q5: Can I abruptly stop this medication?
A: Abrupt discontinuation of atenolol can lead to rebound hypertension or angina. Atenolol should be tapered gradually under medical supervision.
Q6: Is this combination safe in pregnancy?
A: Atenolol + Hydrochlorothiazide is generally not recommended during pregnancy due to the potential risk of fetal growth restriction and other complications.
Q7: What should I do if a patient experiences significant bradycardia?
A: Reduce the dose of atenolol or discontinue the medication. Consider administering atropine if clinically indicated.
Q8: Can this combination be used in patients with renal impairment?
A: Atenolol doses should be adjusted for patients with renal impairment (lower maximum doses depending on CrCl). Hydrochlorothiazide is not recommended if CrCl is less than 30 ml/min.
A: Atenolol can mask the symptoms of hypoglycemia in diabetic patients and may affect glucose metabolism. Careful monitoring is essential.
