Captopril

Cardiovascular Drug

Drug class: Angiotensin Converting Enzyme Inhibitors, ACEI

Captopril (CAPOTEN)（中文：卡托普利）

Pronunciation

Captopril 12.5mg

Captopril 25mg

Common Strengths of Captopril

Captopril is available in the following strengths:

• 6.25 mg
• 12.5 mg
• 25 mg
• 50 mg

Drug Trade Name of Captopril

The brand names for captopril is Capoten.

Mechanism of Action

Captopril is an angiotensin converting enzyme inhibitor (ACE inhibitor).

The beneficial effects of ACE inhibitors appear to result primarily from the suppression of the plasma renin-angiotensin-aldosterone system. Renin is synthesized by the kidneys and released into the circulation where it converts angiotensinogen to angiotensin-I. Angiotensin-I is then converted by angiotensin converting enzyme to angiotensin-II. Angiotensin-II is a potent vasoconstrictor responsible for arterial vasoconstriction and increased blood pressure, as well as for stimulation of the adrenal gland to secrete aldosterone.

Inhibition of ACE results in decreased plasma angiotensin-II, which leads to decreased vasopressor activity and to reduced aldosterone secretion.

Captopril is used in the management of hypertension, in heart failure, after myocardial infarction, and in diabetic nephropathy.

Route of Administration

Captopril in given orally.

Dosages

• Hypertension
  • Adult: Initially 12.5 – 25 mg twice daily, then increased if necessary up to 150 mg daily in 2 divided doses.
  • Elderly: Initially 6.25 mg twice daily, then increased if necessary up to 150 mg daily in 2 divided doses.

• Heart failure
  • Adult: Initially 6.25 – 12.5 mg, 2-3 times a day, then increased if tolerated to up to 150 mg daily in divided doses.

• After myocardial infarction
  • Adult: Initially 6.25 mg daily, then increased to 12.5 mg 3 times a day for 2 days, then increased if tolerated to 25 mg 3 times a day, then increased if tolerated to 75 – 150 mg daily in 2-3 divided doses, doses to be increased gradually.
  • Captopril is used prophylactically in clinically stable patients with symptomatic or asymptomatic left ventricular dysfunction to improve survival, delay the onset of symptomatic heart failure, and reduce recurrent infarction.

• Diabetic nephropathy (microalbuminuria > 30 mg/day) in type 1 diabetes
  • Adult: 75 – 100 mg daily in divided doses

Reductions of blood pressure are usually maximal 60 to 90 minutes after oral administration of an individual dose of captopril. The duration of effect is dose related and may persist for 6 hours to 12 hours. The reduction in blood pressure may be progressive, so to achieve maximal therapeutic effects may take several weeks.

Side Effects

Frequency	Adverse reactions
Common Side Effect	Sleep disorders
	Dry
	Irritating (non-productive) cough and dyspnoea
	Pruritus with or without a rash
	Rash and alopecia
	Abdominal pain
	Nausea
	Constipation
	Diarrhoea
	Dry mouth
	Peptic ulcer
	Dyspepsia
Uncommon Side Effect	Tachycardia
	Angina
	Arrhythmia
	Hypotension
	Raynaud syndrome
	Flush
	Pallor
	Stomatitis
	Small bowel angioedema
	Confusion
	Depression
	Glossitis
	Pancreatitis

Pharmacokinetics

• Captopril is an orally active drug that does not require biotransformation for activity.
• The average minimal absorption is approximately 75%.
• Peak plasma concentrations are reached within 60-90 minutes. The presence of food in the gastrointestinal tract reduces absorption by about 30 – 40%.
• Approximately 25% to 30% of the circulating drug is bound to plasma proteins.
• The apparent elimination half-life of unchanged captopril in blood is about 2 hours. Greater than 95% of the absorbed dose is eliminated in the urine within 24 hours. Impaired renal function could result in drug accumulation. Therefore, in patients with impaired renal function the dose should be reduced and/or dosage interval prolonged.

Drug Management

Safety

For hypertension the first dose should preferably be given at bedtime.

Pregnancy

Should be avoided in pregnancy unless essential.

Breast Feeding

• Should be avoided in the few weeks after delivery, particularly in preterm infants.
  • Risk of profound neonatal hypotension.
• Can be used in mothers breast-feeding older infants if essential.

Renal Impairment

Need to reduce the dose.

• If eGFR >40 mL/minute/1.73 m²
  • Max. initial dose 50 mg
• If eGFR 20 – 40 mL/minute/1.73 m²
  • Max. initial dose 25 mg (do not exceed 100 mg daily)
• If eGFR 10 – 20 mL/minute/1.73 m²
  • Max. initial dose 12.5 mg (do not exceed 75 mg daily)
• If eGFR <10 mL/minute/1.73 m²
  • Max. initial dose 6.25 mg (do not exceed 37.5 mg daily)

Monitoring Requirements

Renal function and electrolytes should be checked before starting ACE inhibitors (or increasing the dose) and monitored during treatment (more frequently if side effects mentioned are present).

Drug Interaction

• Diuretics
  • Prior treatment with high dose diuretics may result in volume depletion and a risk of hypotension when initiating therapy with captopril.
• Potassium sparing diuretics (triamterene, amiloride and spironolactone) or potassium supplement
  • May cause significant increase in serum potassium.

Caution

• Concomitant diuretics
  • first dose hypotension (especially in patients taking high doses of diuretics, on a low-sodium diet, on dialysis, dehydrated , or with heart failure)
• Use with care in those with a history of angioedema
• Use with care in patients with severe or symptomatic aortic stenosis (risk of hypotension)

FAQ

How should I take the tablet?

Captopril is best given on an empty stomach, 1 hour before meal, to increase effectiveness.

What should I avoid while taking?

Should avoid potassium rich foods: captopril has the capacity to increase potassium level in the blood. High levels of potassium can lead to irregular heartbeat. It is better to avoid potassium-rich foods like bananas.

What happens if I miss a dose?

If you forget to take a dose and you usually take captopril:

• Twice a day: take it as soon as you remember unless it is less than 4 hours until your next dose. In this case leave out the missed dose and take your next dose at the usual time
• 3 times a day: leave out that dose and take your next dose at the usual time

Never take 2 doses to make up for a forgotten one.