Captopril
Captopril (中文:卡托普利) is an inhibitor of angiotensin-I converting enzyme (ACE inhibitor).
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
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
The following definitions of frequencies are used:
Very common ≥ 1/10
Common ≥ 1/100 to < 1/10
Uncommon ≥ 1/1,000 to < 1/100
Rare ≥ 1/10,000 to < 1/1,000
Very rare < 1/10,000
| 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.
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 happen 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.
