Captopril

Captopril was the first approved ACE inhibitor and has been in use since the 1980s. It is used to treat high blood pressure, heart failure, after a heart attack, and in diabetic nephropathy.

It usually has to be taken two to three times a day, which is a disadvantage compared with newer ACE inhibitors.

Captopril directly inhibits the ACE enzyme:

Mechanism of action:

• Direct ACE inhibition (not a prodrug)
• Rapid onset of action (15-30 minutes)
• Short duration of action (6-12 hours)
• Lowers blood pressure by dilating blood vessels

Special feature:

• Contains a sulfhydryl group (SH group)
• Fastest onset of action of all ACE inhibitors
• Short half-life requires multiple daily doses

Captopril is suitable for:

• Adults with high blood pressure
• Heart failure
• After a heart attack
• Diabetic nephropathy (type 1 diabetes)

Particularly suitable:

• When a rapid onset of action is desired
• Diagnostic purposes (captopril test for renal artery stenosis)

Not suitable:

• Pregnancy
• Breastfeeding premature infants and during the first weeks after delivery
• History of angioedema
• Patients who prefer a once-daily dose

High blood pressure:

• Starting dose: 12.5-25 mg twice daily
• Usual dose: 25-50 mg twice daily
• Maximum dose: 150 mg daily

Heart failure:

• Starting dose: 6.25-12.5 mg three times daily
• Target dose: 50 mg three times daily

Available strengths:

• 12.5 mg, 25 mg, 50 mg tablets

How to take:

• Two to three times daily
• Take on an empty stomach (1 hour before meals)
• Meals reduce absorption by 30-40%
• Take with water

Important notes:

• Regular laboratory tests (kidneys, potassium, blood count)
• Do not stop abruptly
• Self-monitoring of blood pressure recommended

Captopril must not be taken in the following cases:

• Hypersensitivity to captopril or other ACE inhibitors
• History of angioedema
• Pregnancy in the 2nd and 3rd trimester
• Bilateral renal artery stenosis
• Concomitant use of sacubitril/valsartan (at least 36 hours apart when switching)
• Concomitant use with aliskiren in diabetes mellitus or impaired kidney function (GFR below 60 ml/min/1.73 m²)

Use with caution in:

• Impaired kidney function
• Collagen vascular diseases (increased risk of blood count changes)
• Immunosuppressive therapy
• Aortic stenosis
• High potassium levels

Pregnancy and breastfeeding: Captopril is not recommended in the 1st trimester of pregnancy and is contraindicated in the 2nd and 3rd trimesters. Treatment should not be started during pregnancy. If pregnancy is detected, treatment must be stopped immediately and, if necessary, another therapy started. Captopril is not recommended when breastfeeding premature infants or in the first weeks after delivery. If the infant is older, use during breastfeeding may be considered if treatment is necessary for the mother and the infant is carefully monitored.

Common (1-10%):

• Dry, irritating cough
• Taste disturbances (metallic taste)
• Skin rash
• Dizziness

Uncommon (0.1-1%):

• Drop in blood pressure
• Gastrointestinal complaints
• Proteinuria
• Elevated potassium levels

Rare:

• Angioedema
• Neutropenia/agranulocytosis (especially in renal insufficiency and collagen vascular diseases)
• Severe skin reactions

Special feature: Taste disturbances occur more frequently with captopril than with newer ACE inhibitors, due to the SH group.

Important interactions:

• Potassium-sparing diuretics → hyperkalemia
• NSAIDs → reduced effect, kidney damage
• Lithium → increased levels
• Antacids → reduced absorption of captopril
• Probenecid → increased captopril levels

Food intake: Meals reduce bioavailability by 30-40%. Taking it on an empty stomach is recommended.

Caution:

• Allopurinol (hypersensitivity reactions)
• Procainamide (blood count changes)