Usage
Captopril is prescribed for:
- Hypertension (high blood pressure)
- Heart failure
- Diabetic nephropathy (kidney disease caused by diabetes)
- Left ventricular dysfunction after myocardial infarction (heart attack)
Pharmacological Classification: Angiotensin-Converting Enzyme (ACE) inhibitor.
Mechanism of Action: Captopril blocks the conversion of angiotensin I to angiotensin II, a potent vasoconstrictor. This leads to vasodilation (widening of blood vessels), reduced blood pressure, and decreased workload on the heart. It also reduces aldosterone secretion, which leads to decreased sodium and water retention.
Alternate Names
Captopril is the generic name. Brand names include Capoten.
How It Works
Pharmacodynamics: Captopril’s primary effect is to lower blood pressure and reduce cardiac afterload (the resistance the heart must overcome to pump blood). It achieves this by preventing the formation of angiotensin II, a potent vasoconstrictor, leading to vasodilation and a decrease in blood pressure. It also reduces aldosterone secretion, leading to a decrease in sodium and water retention.
Pharmacokinetics:
- Absorption: Absorbed rapidly from the gastrointestinal tract, absorption reduced by food.
- Metabolism: Minimal hepatic metabolism.
- Elimination: Primarily renal excretion, with a half-life of about 2 hours.
Mode of Action: Captopril competitively inhibits ACE, preventing the conversion of angiotensin I to angiotensin II.
Receptor Binding, Enzyme Inhibition, or Neurotransmitter Modulation: Inhibits ACE enzyme activity.
Elimination Pathways: Primarily renal excretion as captopril and captopril disulfide metabolite.
Dosage
Standard Dosage
Adults:
- Hypertension: Initial dose 25 mg orally two to three times a day. Titrate upwards at 1-2 week intervals as needed to a maximum of 450 mg/day.
- Heart Failure: Initial dose 6.25-12.5 mg orally two or three times a day. Titrate up to a target maintenance dose of 50 mg three times a day or higher as tolerated, to a maximum of 450 mg/day.
- Post-Myocardial Infarction: Initial dose 6.25 mg orally once as early as three days post-MI, followed by 12.5 mg three times daily. Increase to 25 mg three times daily, and then to a target dose of 50 mg three times daily over several weeks as tolerated, to a maximum of 450 mg/day.
- Diabetic Nephropathy: 25 mg orally three times a day, titrated as needed.
Children:
- Neonates: 0.05-0.1 mg/kg/dose every 8-24 hours, titrate up to 0.5 mg/kg/dose every 6-24 hours.
- Infants: 0.15-0.3 mg/kg/dose, titrate upward to a maximum of 6 mg/kg/day in divided doses.
- Children: 0.3-0.5 mg/kg/dose, titrate to a maximum of 6 mg/kg/day in divided doses every 6-12 hours.
- Adolescents: 12.5-25 mg/dose every 8-12 hours, may increase by 25 mg/dose every 1-2 weeks to a maximum of 450 mg/day.
Special Cases:
- Elderly Patients: Initiate therapy with a lower starting dose (e.g., 6.25 mg twice daily) and titrate cautiously due to potential for reduced renal function.
- Patients with Renal Impairment: Reduce dosage based on creatinine clearance.
- Patients with Hepatic Dysfunction: No specific dosage adjustments are typically required.
- Patients with Comorbid Conditions: Dosage adjustments may be necessary depending on the specific comorbidity.
Clinical Use Cases
Captopril is not typically indicated for use in clinical settings such as intubation, surgical procedures, mechanical ventilation, or intensive care unit (ICU) use for the primary purpose of those conditions. It might be continued or adjusted during those situations for existing conditions like heart failure or hypertension.
Dosage Adjustments
Dose modifications may be required in patients with renal or hepatic impairment, or in patients with certain comorbidities. Titrate cautiously in these populations and monitor closely.
Side Effects
Common Side Effects
- Cough
- Dizziness
- Hypotension (low blood pressure)
- Rash
- Altered taste
- Hyperkalemia (high potassium)
Rare but Serious Side Effects
- Angioedema (swelling of face, lips, tongue, throat)
- Neutropenia (low white blood cell count)
- Proteinuria (protein in the urine)
- Renal failure
Long-Term Effects
- Renal dysfunction
- Electrolyte imbalances
Adverse Drug Reactions (ADR)
- Angioedema
- Neutropenia
- Hypotension
Contraindications
- Hypersensitivity to captopril or other ACE inhibitors
- History of angioedema related to ACE inhibitor therapy
- Bilateral renal artery stenosis or stenosis of the artery to a solitary kidney
- Pregnancy (second and third trimesters)
- Concomitant use of aliskiren in patients with diabetes or renal impairment
- Concomitant use of sacubitril/valsartan
Drug Interactions
- Diuretics: Increased risk of hypotension.
- Potassium supplements or potassium-sparing diuretics: Increased risk of hyperkalemia.
- NSAIDs: Reduced antihypertensive effect and increased risk of renal impairment.
- Lithium: Increased lithium levels.
- Aliskiren: Increased risk of hypotension, hyperkalemia, and renal impairment.
- Sacubitril/valsartan: Increased risk of angioedema.
- mTOR inhibitors: Increased risk of angioedema.
Pregnancy and Breastfeeding
- Pregnancy Safety Category: Category D (first trimester), Category X (second and third trimesters) - contraindicated. ACE inhibitors can cause fetal harm or death.
- Breastfeeding: Captopril is present in breast milk. Alternate safer options or discontinuation of breastfeeding may be advisable.
Drug Profile Summary
- Mechanism of Action: ACE inhibitor, reduces angiotensin II and aldosterone.
- Side Effects: Cough, dizziness, hypotension, rash, altered taste, hyperkalemia. Rare but serious: angioedema, neutropenia, renal failure.
- Contraindications: Hypersensitivity, history of angioedema, bilateral renal artery stenosis, pregnancy (2nd/3rd trimester), concomitant use of aliskiren (in diabetes or renal impairment) or sacubitril/valsartan.
- Drug Interactions: Diuretics, potassium supplements, NSAIDs, lithium, aliskiren, sacubitril/valsartan, mTOR inhibitors.
- Pregnancy & Breastfeeding: Contraindicated in 2nd/3rd trimester of pregnancy; caution advised during breastfeeding.
- Dosage: Varies depending on indication; typical starting dose 25 mg two or three times daily.
- Monitoring Parameters: Blood pressure, renal function, potassium levels.
Popular Combinations
Captopril is often combined with a thiazide diuretic like hydrochlorothiazide (e.g., Capozide). This combination offers synergistic antihypertensive effects.
Precautions
- General Precautions: Monitor renal function, potassium levels, and blood pressure.
- Specific Populations: Use with caution in the elderly and patients with renal impairment. Contraindicated in pregnancy (2nd/3rd trimesters). Caution during breastfeeding.
- Lifestyle Considerations: Excessive alcohol intake and dehydration may exacerbate hypotension.
FAQs (Frequently Asked Questions)
Q1: What is the recommended dosage for Captopril?
A: The dosage varies depending on the indication and patient characteristics. Common starting doses are 25 mg two or three times daily for hypertension and 6.25-12.5 mg two or three times daily for heart failure. Dosage adjustments are required for renal impairment.
Q2: What is the most serious side effect of Captopril?
A: Angioedema, a serious allergic reaction involving swelling of the face, lips, tongue, and throat, requiring immediate medical attention.
Q3: Can Captopril be used in pregnancy?
A: Captopril is contraindicated during the second and third trimesters of pregnancy due to risk of fetal harm. It is generally avoided in the first trimester as well.
Q4: What are the common drug interactions with Captopril?
A: Diuretics, potassium supplements, NSAIDs, lithium, aliskiren, and sacubitril/valsartan.
Q5: How does Captopril affect potassium levels?
A: Captopril can cause hyperkalemia (elevated potassium levels), so monitoring is essential, especially in patients with renal impairment or those taking potassium supplements.
Q6: What should patients be advised about lifestyle while taking Captopril?
A: Patients should avoid excessive alcohol intake and dehydration, as these can exacerbate hypotension. They should also be cautious when rising from a lying or sitting position.
Q7: What should be monitored in patients taking Captopril?
A: Blood pressure, renal function (serum creatinine, blood urea nitrogen), and potassium levels.
Q8: Is Captopril safe for patients with liver disease?
A: Generally, yes, but caution is advised. Dosage adjustments are usually not required but close monitoring is important.
Q9: What are the symptoms of an allergic reaction to Captopril?
A: Skin rash, itching, swelling (particularly of the face, lips, tongue or throat), dizziness, difficulty breathing. Seek immediate medical attention if any of these occur.
