Usage
- Medical Conditions: Captopril + Hydrochlorothiazide is prescribed for the treatment of hypertension (high blood pressure). It is used when treatment with either drug alone does not adequately control blood pressure.
- Pharmacological Classification: Combined Antihypertensive; ACE inhibitor/Thiazide diuretic combination.
- Mechanism of Action: This combination medication lowers blood pressure through two distinct mechanisms. Captopril, an angiotensin-converting enzyme (ACE) inhibitor, prevents the formation of angiotensin II, a potent vasoconstrictor. This leads to vasodilation and reduced blood pressure. Hydrochlorothiazide, a thiazide diuretic, increases the excretion of sodium and water by the kidneys, reducing blood volume and further lowering blood pressure.
Alternate Names
- Capozide (brand name)
- Captopril/hydrochlorothiazide
How It Works
- Pharmacodynamics: Captopril inhibits ACE, reducing angiotensin II formation, leading to vasodilation, decreased aldosterone secretion, and reduced peripheral vascular resistance. Hydrochlorothiazide inhibits sodium reabsorption in the distal convoluted tubule of the nephron, promoting diuresis and reducing blood volume.
- Pharmacokinetics: Captopril is rapidly absorbed orally, reaching peak plasma concentrations within 1 hour. It is primarily excreted by the kidneys. Hydrochlorothiazide is also well-absorbed orally and is excreted unchanged by the kidneys.
- Mode of Action: Captopril competitively binds to and inhibits ACE, preventing the conversion of angiotensin I to angiotensin II. Hydrochlorothiazide inhibits the sodium-chloride cotransporter in the distal convoluted tubule, impairing sodium reabsorption and increasing water excretion.
- Elimination Pathways: Both captopril and hydrochlorothiazide are primarily eliminated through renal excretion.
Dosage
Standard Dosage
Adults:
- Initial dose: 25 mg captopril/15 mg hydrochlorothiazide once daily, taken 1 hour before meals.
- Maintenance dose: 50 mg captopril/25 mg hydrochlorothiazide once daily.
- Maximum dose: 150 mg captopril/50 mg hydrochlorothiazide per day.
- Dosage adjustments should be made at intervals of 6-8 weeks, based on the patient’s response.
Children:
- Safety and efficacy not established for use in children. There is no current recommendation to use this drug for patients under 18 years of age.
Special Cases:
- Elderly Patients: Start with a lower dose (e.g., 25mg captopril/12.5mg hydrochlorothiazide) and titrate cautiously.
- Patients with Renal Impairment: For mild to moderate renal impairment (creatinine clearance 30-80 mL/min), start with 25 mg captopril/12.5 mg hydrochlorothiazide once daily. Contraindicated in severe renal impairment (creatinine clearance <30 mL/min).
- Patients with Hepatic Dysfunction: Use with caution. Dose adjustment may be necessary. Contraindicated in severe hepatic impairment.
- Patients with Comorbid Conditions: For patients with diabetes, avoid concomitant use with aliskiren. For other comorbid conditions like congestive heart failure, monitor closely for hypotension and electrolyte imbalances.
Clinical Use Cases
- This combined drug is designed specifically for hypertension. There are no clinical use cases for intubation, surgical procedures, mechanical ventilation, ICU use, or emergency situations.
Dosage Adjustments
- Adjust dosage based on blood pressure response, renal function, and presence of other medical conditions.
Side Effects
Common Side Effects
- Cough
- Dizziness
- Lightheadedness
- Taste changes
- Rash
- Itching
Rare but Serious Side Effects
- Angioedema (swelling of face, lips, tongue, throat, and/or extremities)
- Severe hypotension
- Acute renal failure
- Agranulocytosis (dangerously low white blood cell count)
- Hepatotoxicity
- Hyperkalemia
Long-Term Effects
- Electrolyte imbalances (e.g., hypokalemia, hyponatremia)
- Renal impairment
Adverse Drug Reactions (ADR)
- Angioedema
- Severe hypotension
- Agranulocytosis
Contraindications
- Hypersensitivity to captopril, hydrochlorothiazide, other ACE inhibitors, or sulfonamides
- History of angioedema related to ACE inhibitor therapy
- Hereditary/idiopathic angioedema
- Anuria
- Severe renal impairment (CrCl < 30 mL/min)
- Severe hepatic impairment
- Pregnancy (second and third trimesters)
- Concomitant use with aliskiren in patients with diabetes or renal impairment (GFR < 60 mL/min/1.73 m²)
- Concomitant use with or within 36 hours of sacubitril/valsartan
Drug Interactions
- Aliskiren (contraindicated in patients with diabetes or renal impairment)
- Sacubitril/valsartan (contraindicated within 36 hours of switching)
- Potassium supplements or salt substitutes containing potassium (may cause hyperkalemia)
- Lithium (increased risk of lithium toxicity)
- Other antihypertensive medications (additive hypotensive effects)
- NSAIDs (may decrease antihypertensive effect and increase risk of renal impairment)
Pregnancy and Breastfeeding
- Pregnancy: Contraindicated during the second and third trimesters due to risk of fetal harm. Not recommended during the first trimester.
- Breastfeeding: Not recommended. The drug is excreted in breast milk.
Drug Profile Summary
- Mechanism of Action: ACE inhibition (captopril) and diuresis (hydrochlorothiazide) leading to reduced blood pressure.
- Side Effects: Cough, dizziness, lightheadedness, angioedema, hypotension, renal impairment.
- Contraindications: Hypersensitivity, angioedema history, renal/hepatic impairment, pregnancy.
- Drug Interactions: Aliskiren, sacubitril/valsartan, potassium supplements, lithium, NSAIDs.
- Pregnancy & Breastfeeding: Contraindicated in second and third trimesters of pregnancy; not recommended while breastfeeding.
- Dosage: Adults: Initial 25/15 mg once daily, maintenance 50/25 mg once daily, max 150/50 mg daily.
- Monitoring Parameters: Blood pressure, renal function, electrolytes (potassium, sodium).
Popular Combinations
- This medication is itself a combination. The addition of other antihypertensive medications may be considered if blood pressure control is not achieved, but it requires careful monitoring for additive effects and interactions.
Precautions
- General Precautions: Monitor renal function and electrolytes, especially potassium.
- Specific Populations: Caution in elderly patients and patients with renal or hepatic impairment. Contraindicated in pregnancy (second and third trimesters). Not recommended during breastfeeding.
- Lifestyle Considerations: Advise patients to limit alcohol intake, as it can worsen side effects.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Captopril + Hydrochlorothiazide?
A: Initial dose is 25 mg captopril/15 mg hydrochlorothiazide once daily. Maintenance dose is typically 50 mg captopril/25 mg hydrochlorothiazide once daily. Maximum dose is 150 mg captopril/50 mg hydrochlorothiazide per day. Dosage adjustments may be needed based on individual patient response and the presence of other medical conditions.
Q2: What are the common side effects of Captopril + Hydrochlorothiazide?
A: Common side effects include cough, dizziness, lightheadedness, taste disturbances, and rash.
Q3: Can Captopril + Hydrochlorothiazide be used during pregnancy?
A: This medication is contraindicated during the second and third trimesters of pregnancy due to the risk of fetal harm. It is generally not recommended during the first trimester.
Q4: What are the serious side effects of Captopril + Hydrochlorothiazide?
A: Serious side effects include angioedema, severe hypotension, acute renal failure, agranulocytosis, and hepatotoxicity.
Q5: How does Captopril + Hydrochlorothiazide interact with other medications?
A: It can interact with medications such as aliskiren, sacubitril/valsartan, potassium supplements, lithium, and NSAIDs. Inform patients about potential interactions with any other prescribed or over-the-counter medications.
Q6: What are the contraindications to using Captopril + Hydrochlorothiazide?
A: Contraindications include hypersensitivity to the drug components, history of angioedema related to ACE inhibitors, severe renal or hepatic impairment, pregnancy (second and third trimesters), and concomitant use with aliskiren in specific patient populations.
Q7: Can Captopril + Hydrochlorothiazide be used in patients with renal impairment?
A: It can be used with caution in patients with mild to moderate renal impairment, starting at a lower dose. It is contraindicated in severe renal impairment.
Q8: What should be monitored in patients taking Captopril + Hydrochlorothiazide?
A: Blood pressure, renal function, and electrolyte levels (particularly potassium and sodium) should be regularly monitored.
Q9: Can this medication be used in patients with diabetes?
A: It can be used in patients with diabetes but concomitant use of aliskiren should be avoided. Close monitoring of blood pressure, renal function, and electrolytes is essential.
Q10: What patient education should be provided when prescribing this medication?
A: Patients should be informed about potential side effects, including cough, dizziness, and the signs of angioedema. They should be advised to avoid potassium supplements and salt substitutes unless specifically directed by their physician. Patients should also be informed about potential drug interactions and the importance of consistent monitoring. The risk of fetal harm during pregnancy should be clearly explained.
