Captopril

Pronunciation

Captopril 12.5mg

Captopril 25mg

Generic Name:	Captopril
Class:	Cardiovascular Drug
Subclass:	ACE inhibitors
Legal Classification:	P1S1S3

Drug Names

Generic Name 藥物化學名稱	HA Code 藥物代碼	Legal Classification法律藥物分類
Captopril Tablet 6.25mg		P1S1S3
Captopril Tablet 12.5mg	CAPT03	P1S1S3
Captopril Tablet 25mg	CAPT01	P1S1S3
Captopril Tablet 50mg		P1S1S3

Mechanism of Action

Captopril is an inhibitor of angiotensin-I converting enzyme (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.

Dosage

Hypertension

• Adult: initially 12.5 – 25 mg twice daily, then increased if necessary up to 150mg 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, 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.

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

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

System Organ Class	Frequency	Adverse reactions
Psychiatric disorders	Common	Sleep disorders
	Very rare	Confusion, depression
Respiratory disorders	Common	Dry, irritating (non-productive) cough and dyspnoea
Skin disorders	Common	Pruritus with or without a rash, rash and alopecia
Gastro-intestinal disorders	Common	Abdominal pain, nausea, constipation, diarrhoea, dry mouth, peptic ulcer, dyspepsia
	Rare	Stomatitis, small bowel angioedema
	Very rare	Glossitis, pancreatitis
Cardiac disorders	UnCommon	Hypotension Raynaud syndrome Flush pallor

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 avoid 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 reduce dose;

max. initial dose 50 mg if eGFR above 40ml/minute/1.73 m2

max. initial dose 25 mg (do not exceed 100 mg daily) if eGFR 20 – 40 ml/ minute/1.73 m2

max. initial dose 12.5 mg (do not exceed 75 mg daily) if eGFR 10 – 20 ml/ minute/1.73 m2

max. initial dose 6.25 mg (do not exceed 37.5 mg daily) if eGFR < 10 ml/ minute/1.73 m2

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).

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.