Captopril

High blood pressure, heart failure, and diabetic kidney disease are serious conditions requiring careful long-term management. Captopril tablets are a prescription ACE inhibitor used to treat hypertension and congestive heart failure, following a heart attack and to protect kidney function in patients with diabetic nephropathy. Captopril was one of the first ACE inhibitors to be developed and has an established clinical record spanning several decades. It is taken two or three times daily, which distinguishes it from most newer ACE inhibitors that are taken once daily. A prescription can only be issued following a clinical consultation with a registered prescriber.

Captopril tablets are an oral prescription medicine containing captopril as the active ingredient. Captopril belongs to the angiotensin-converting enzyme (ACE) inhibitor class of medicines. ACE inhibitors are widely used in the management of cardiovascular and renal conditions. Captopril was the first orally active ACE inhibitor to be developed and licensed, and its clinical use has been extensively studied since its introduction in the late 1970s.

Captopril is licensed in the United Kingdom for four indications: treatment of hypertension (high blood pressure); treatment of congestive heart failure in combination with diuretics and, where appropriate, digitalis; following a myocardial infarction (heart attack) in clinically stable patients with left ventricular dysfunction; and treatment of diabetic nephropathy (kidney disease caused by diabetes) in patients with Type 1 diabetes mellitus and microalbuminuria above 30mg per day. It is available in three strengths: 12.5mg, 25mg, and 50mg tablets.

All clinical information on this page is drawn from the current UK Summary of Product Characteristics for captopril tablets.

Important: Captopril must not be used during pregnancy. ACE inhibitors can cause serious harm to the developing foetus, particularly during the second and third trimesters, including kidney damage, skull defects, and, in severe cases, death of the unborn baby. If you become pregnant while taking captopril, stop taking it and contact your prescriber immediately. Effective contraception is essential for women of childbearing potential during treatment.

Captopril works by inhibiting angiotensin-converting enzyme, a key enzyme in the renin-angiotensin-aldosterone system. This system regulates blood pressure, fluid balance, and kidney function. When ACE is inhibited, less angiotensin II is produced. Angiotensin II is a powerful hormone that causes blood vessels to narrow and stimulates aldosterone release, which promotes sodium and water retention.

Effect on Blood Pressure

By reducing angiotensin II production, captopril causes blood vessels to relax and widen, reducing peripheral vascular resistance and lowering blood pressure. ACE inhibition also reduces aldosterone levels, which decreases sodium and water retention. Together, these effects produce a sustained reduction in blood pressure. Captopril has a relatively short duration of action compared to more modern ACE inhibitors, which is why it is taken two or three times daily rather than once.

Effect on Heart Failure

In congestive heart failure, captopril reduces the workload on the failing heart by lowering the pressure against which it must pump (afterload reduction) and by reducing the volume of fluid that the heart must handle (preload reduction). This improves cardiac output, reduces symptoms such as breathlessness and ankle swelling, and has been shown to reduce mortality in patients with heart failure.

Effect on Diabetic Nephropathy

In patients with Type 1 diabetes and microalbuminuria, captopril reduces proteinuria and slows the progression of kidney disease. ACE inhibitors reduce intraglomerular pressure within the kidneys, which reduces the leakage of protein into the urine and helps preserve kidney function over time. This renoprotective effect is independent of its blood pressure-lowering effect and is a specific licensed indication for captopril.

Always take captopril exactly as your prescriber instructs. The information below summarises key points from the current UK SmPC. Read the Patient Information Leaflet supplied with your medicine before starting treatment.

• Captopril should be taken 30 to 60 minutes before meals. Food significantly reduces the absorption of captopril, so taking it on an empty stomach helps ensure a consistent and effective dose.
• Take captopril two or three times daily as directed by your prescriber, depending on the condition being treated and the dose prescribed.
• If you miss a dose, take it as soon as you remember, provided your next scheduled dose is not due soon. If it is nearly time for your next dose, skip the missed dose and continue with your normal schedule. Do not take two doses at the same time.
• Do not stop taking captopril without speaking to your prescriber first. Stopping an ACE inhibitor suddenly may cause your blood pressure to rise or your heart failure to worsen.
• Avoid potassium-containing salt substitutes and potassium supplements unless your prescriber has specifically advised them, as captopril can raise blood potassium levels.

Captopril tablets are available in three strengths through this service. The appropriate dose will be determined by your prescriber based on the condition being treated, your blood pressure, kidney function, and clinical response. Because captopril has a short duration of action, doses are typically given two or three times daily rather than once.

Captopril 12.5mg Tablets

The 12.5mg tablet is used as a low starting dose, particularly in patients who are volume-depleted, those with severe heart failure, or those initiating treatment under close supervision. For hypertension, treatment may begin at 12.5mg two or three times daily to minimise the risk of a significant first-dose fall in blood pressure. For heart failure, 6.25mg or 12.5mg two or three times daily is the typical starting dose, increased gradually under clinical supervision.

Captopril 25mg Tablets

The 25mg tablet is a commonly used maintenance strength for hypertension and heart failure. For hypertension, 25mg two or three times daily may provide adequate blood pressure control in many patients. For heart failure, the dose is titrated upward from lower starting doses toward the target maintenance dose. The 25mg strength allows dosing flexibility during titration.

Captopril 50mg Tablets

The 50mg tablet is used when higher doses are required for adequate blood pressure or heart failure control. For hypertension, the usual maintenance dose is 25mg to 50mg two or three times daily, with a maximum of 150mg per day. For heart failure, the usual target maintenance dose is 25mg to 50mg three times daily. For diabetic nephropathy, captopril 25mg three times daily is the established dose. All dose adjustments are made by your prescriber. Do not increase your dose without medical advice.

Like all medicines, captopril can cause side effects, although not everyone experiences them. The information below is based on the current UK SmPC. Refer to the Patient Information Leaflet for the full list.

Common Side Effects (may affect up to 1 in 10 people)

• A persistent dry cough - this is one of the most frequently reported side effects of all ACE inhibitors, including captopril. It is caused by a build-up of bradykinin in the airways. The cough is dry, tickly, and does not produce phlegm. It occurs in a significant proportion of patients and does not usually resolve on its own while treatment continues.
• Dizziness or lightheadedness, particularly when standing up quickly (postural hypotension). This is more likely after the first dose or after a dose increase, and in patients who are volume-depleted.
• Raised blood potassium levels (hyperkalaemia), which can affect heart rhythm.
• Impaired kidney function, particularly in patients with pre-existing kidney disease or renal artery stenosis.
• Fatigue and tiredness.

Uncommon Side Effects (may affect up to 1 in 100 people)

• Taste disturbance or loss of taste (dysgeusia) - Captopril can affect the sense of taste in some patients. This usually resolves within a few weeks of treatment.
• Skin rash, which may be itchy.
• Nausea, stomach discomfort, or loss of appetite.
• Raised blood urea and creatinine, indicating changes in kidney function.

Serious Side Effects: Seek Urgent Medical Attention

Contact your prescriber or go to your nearest accident and emergency department promptly if you experience any of the following:

• Angioedema - sudden swelling of the face, lips, tongue, throat, hands, or feet. This is a rare but potentially life-threatening reaction. Angioedema of the tongue or throat can obstruct breathing. If you experience swelling of the face or throat, seek emergency medical help immediately. Do not wait to see if it resolves. Angioedema is more common with ACE inhibitors than with ARBs.
• A marked reduction in urine output, which may indicate acute kidney injury.
• Symptoms of very high potassium such as muscle weakness, an irregular heartbeat, or tingling.
• Signs of neutropenia or agranulocytosis such as fever, sore throat, mouth ulcers, or unusual infections. Captopril can rarely reduce white blood cell counts, particularly in patients with kidney impairment or connective tissue disease.
• Severe skin reactions including blistering or peeling.

Report any suspected side effect to your prescriber or pharmacist or via the MHRA Yellow Card scheme at yellowcard.mhra.gov.uk.

Captopril Tablets May Be Suitable If You:

• Are an adult with hypertension who requires antihypertensive treatment and has been assessed as suitable for ACE inhibitor therapy.
• Have congestive heart failure and are being managed with diuretics and, where appropriate, digitalis.
• Are a clinically stable adult following a myocardial infarction with left ventricular dysfunction.
• Have Type 1 diabetes mellitus with microalbuminuria above 30mg per day and diabetic nephropathy requiring renoprotective treatment.
• Are already prescribed captopril and require a repeat prescription through an online prescribing service.

Captopril Tablets Are Not Suitable If You:

• Are pregnant or planning to become pregnant - captopril must not be used during pregnancy.
• Have a history of ACE inhibitor-induced angioedema, or hereditary or idiopathic angioedema.
• Have bilateral renal artery stenosis or renal artery stenosis in a single functioning kidney.
• Are taking aliskiren alongside captopril if you have diabetes or kidney impairment (eGFR below 60 ml/min/1.73m2).
• Have severe kidney impairment or significant kidney disease not listed as an indication for captopril.
• Have a known allergy or hypersensitivity to captopril, any other ACE inhibitor, or any excipient listed in the SmPC.
• Are under 18 years of age (this service is for adults only).

Cautions

Particular caution is required in patients with aortic stenosis or hypertrophic obstructive cardiomyopathy, as the blood pressure lowering effect may cause a significant reduction in cardiac output. Caution is also required in patients with collagen vascular disease (such as systemic lupus erythematosus or scleroderma) and those taking immunosuppressant medicines, as the risk of neutropenia is higher in these groups. Patients with kidney impairment require careful monitoring and dose adjustment. Older patients and those taking diuretics are at greater risk of a significant first-dose fall in blood pressure.

Important Drug Interactions

Captopril can interact with a number of commonly prescribed medicines. Tell your prescriber about all medicines you take, including over-the-counter products and herbal supplements. The following interactions are of particular clinical importance:

• Potassium-sparing diuretics (such as spironolactone or amiloride), potassium supplements, or potassium-containing salt substitutes: combining these with captopril significantly increases the risk of hyperkalaemia.
• ARBs and aliskiren: combining captopril with an ARB or aliskiren increases the risk of hypotension, hyperkalaemia, and kidney impairment. The combination of an ACE inhibitor and an ARB is not recommended in most patients.
• NSAIDs such as ibuprofen: these can reduce the antihypertensive effect of captopril and significantly increase the risk of kidney problems, including acute kidney injury.
• Lithium: captopril can increase lithium levels, raising the risk of lithium toxicity. Close monitoring is required.
• Diuretics: patients already taking diuretics, particularly those who are volume-depleted, are at risk of a significant first-dose fall in blood pressure with captopril. The diuretic dose may need to be reduced before starting captopril.
• Antidiabetic medicines, including insulin: ACE inhibitors may enhance the blood glucose-lowering effect, increasing the risk of hypoglycaemia. Blood glucose monitoring is particularly important at the start of treatment.

This is not a complete list of interactions. Your prescriber will carry out a full clinical assessment, including a review of your current medicines, before any prescription is considered.

Captopril is a prescription-only medicine. The clinical consultation is the essential first step. A prescription will only be issued if a registered prescriber determines, based on their individual assessment of your circumstances, that captopril is clinically appropriate for you.

During your online consultation with Pharmacy Planet, a registered prescriber will review your clinical information. This includes your blood pressure readings or cardiac and renal history, kidney function, potassium levels, current medicines, and any history of ACE inhibitor-related side effects. Because captopril requires periodic monitoring of kidney function and electrolytes, the prescriber will also assess whether adequate monitoring is in place before considering whether to issue a prescription.

Not all consultations will result in a prescription being issued. The prescriber may recommend a different dose or a different medicine or suggest that a face-to-face appointment with your GP or specialist is more appropriate. This process is designed to ensure your safety.

If you are already being managed for hypertension, heart failure, or diabetic nephropathy by your GP or a hospital team, please keep them informed of all medicines you are taking, including any prescribed through online services.

• Store below 30°C.
• Store in the original packaging to protect from light and moisture.
• Keep out of the sight and reach of children.
• Do not use after the expiry date printed on the packaging.
• Do not dispose of medicines via household waste or wastewater. Return unused or out-of-date tablets to your pharmacist for safe disposal.

Full storage instructions are provided in the Patient Information Leaflet supplied with your medicine.

The table below compares commonly prescribed ACE inhibitor tablets and capsules available at Pharmacy Planet. All are prescription-only medicines that act on the renin-angiotensin system to lower blood pressure.

Important: This comparison is for general information only and does not replace medical advice. A prescriber will decide which treatment is suitable for you following an online consultation.

Pharmacy Planet is a GPhC-registered pharmacy providing prescription medicines through a clinically led consultation process. Our registered prescribers and pharmacists are committed to patient safety, responsible prescribing, and accurate patient information.

Our pharmacy team is available to answer questions about captopril, ACE inhibitor therapy, or cardiovascular and renal health more broadly. We are committed to providing clear, honest information to support you in managing your health safely and with confidence.

References

1. Electronic Medicines Compendium (eMC). Captopril 12.5mg, 25mg and 50mg Tablets — Summary of Product Characteristics. https://www.medicines.org.uk/emc. Accessed August 2026.
2. National Institute for Health and Care Excellence (NICE). Hypertension in adults: diagnosis and management. NICE guideline NG136. https://www.nice.org.uk/guidance/ng136. Accessed August 2026.
3. National Institute for Health and Care Excellence (NICE). Chronic heart failure in adults: diagnosis and management. NICE guideline NG106. https://www.nice.org.uk/guidance/ng106. Accessed August 2026.
4. NHS. Captopril. https://www.nhs.uk/medicines/captopril. Accessed August 2026.
5. Joint Formulary Committee. British National Formulary (BNF). Captopril. BMJ Group and Pharmaceutical Press. https://bnf.nice.org.uk. Accessed August 2026.
6. Medicines and Healthcare products Regulatory Agency (MHRA). Yellow Card — report a side effect. https://yellowcard.mhra.gov.uk. Accessed August 2026.