Captopril

Captopril was the first orally active ACE inhibitor and remains a useful option in specific clinical scenarios, despite largely being replaced by longer-acting agents such as ramipril and lisinopril for routine hypertension management. Its short duration of action and rapid onset make it particularly useful when quick, titratable blood pressure control is needed.

Historical significance

Captopril revolutionised the treatment of hypertension and heart failure when it was introduced in the 1980s. It demonstrated for the first time that inhibiting the renin-angiotensin system could reduce mortality in heart failure (SAVE and ISIS-4 trials), paving the way for the entire class of ACE inhibitors that followed.

When is captopril still used?

Captopril is valued for its rapid onset (15 to 30 minutes) and short half-life, which allows for precise dose titration in unstable situations. It is used for hypertensive urgencies, in the early post-myocardial infarction period, and during the initiation phase of ACE inhibitor therapy in heart failure when careful dose titration is needed.

How to Take Captopril

Take captopril on an empty stomach, 30 to 60 minutes before a meal, as food reduces absorption by around 30 to 40%. Because captopril has a shorter duration of action than most other ACE inhibitors, it is usually taken two to three times daily. Take tablets at evenly spaced intervals throughout the day.

Swallow each tablet whole with a glass of water. Your doctor will start you on a low dose and increase it gradually depending on your blood pressure response and kidney function. Common starting doses are 6.25 to 12.5 mg two to three times daily, rising to a usual maintenance dose of 25 to 50 mg two to three times daily.

Taste Disturbance

A metallic or salty taste is a recognised side effect of captopril specifically, related to its sulphydryl chemical group. It is less common with newer ACE inhibitors. The taste disturbance usually improves if you carry on taking the medication, but let your doctor know if it is persistent or troublesome.

Hypertension: start at 12.5 mg two to three times daily, titrate upward. Heart failure: start at 6.25 mg three times daily, titrate to a target of 50 mg three times daily. Post-MI: start at 6.25 mg, increasing to 150 mg daily in divided doses.

Common Side Effects

• Dry, persistent cough (a class effect of all ACE inhibitors)
• Dizziness or light-headedness, particularly on standing
• Taste disturbance (metallic or salty taste — specific to captopril)
• Low blood pressure (hypotension), especially after the first dose
• Skin rash
• Raised blood potassium levels (hyperkalaemia)

The ACE Inhibitor Cough

The dry cough caused by captopril and other ACE inhibitors is thought to result from a build-up of bradykinin in the airways. It affects around 10 to 15% of people and does not indicate a serious problem, but it can be persistent. If the cough is intolerable, your doctor may switch you to an angiotensin receptor blocker (ARB) such as candesartan, which works in a similar way without causing cough.

Seek immediate medical attention if you develop swelling of the face, lips, tongue, or throat — this is a rare but potentially life-threatening reaction called angioedema.

Monitor renal function and potassium after starting or changing the dose. First-dose hypotension is possible, especially in volume-depleted patients or those on diuretics. Consider giving the first dose at bedtime to reduce this risk.

Angioedema

ACE inhibitors can rarely cause angioedema (swelling of the face, lips, tongue, or throat). This is a medical emergency. Discontinue immediately and never rechallenge.

Contraindicated in pregnancy, history of ACE inhibitor-induced angioedema, hereditary or idiopathic angioedema, bilateral renal artery stenosis, and known hypersensitivity to captopril or any ACE inhibitor.