A short-acting ACE inhibitor
Captopril
The original, short-acting ACE inhibitor for high blood pressure and heart failure; now less used, taken more than once a day, and avoided in pregnancy.
What is Captopril?
Captopril was the first ACE inhibitor developed and remains a member of this widely used class for high blood pressure and heart failure with a reduced pumping function. It relaxes blood vessels and reduces strain on the heart.
Education and reference only. This is a plain-language guide to Captopril — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Captopril was the first ACE inhibitor developed and remains a member of this widely used class for high blood pressure and heart failure with a reduced pumping function. Because it is short-acting, it usually has to be taken more than once a day, which is one reason newer, longer-acting ACE inhibitors (taken once daily) have largely replaced it in everyday use. It still has its place — for example where a short-acting medicine is wanted — and the same class principles and cautions apply. In the UK and US the active ingredient and the original brand (Capoten) are the same; generic captopril is identical.
How it works
Captopril blocks the angiotensin-converting enzyme (ACE), which the body uses to make angiotensin II — a hormone that tightens blood vessels and makes the body hold on to salt and water. With less angiotensin II, blood vessels relax and fluid load falls, so blood pressure drops and the heart has less to work against. The same effect reduces the pressure inside the kidney's filters. Captopril acts and clears quickly, so its effect comes on and wears off faster than longer-acting ACE inhibitors, which is why it is usually divided through the day.
Company & origin
Originated / developed by: Squibb.
Captopril, the first orally active ACE inhibitor, was designed by David Cushman and Miguel Ondetti at Squibb in the US (synthesized around 1975, inspired by snake venom peptides) and was approved by the FDA in 1981, marketed as Capoten.
What it treats
Conditions Captopril is used for
Practical use
How to take Captopril
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Take captopril regularly as prescribed; it is usually taken more than once a day because it is short-acting.
- Stand up slowly, particularly with the first doses, as blood pressure can drop and cause dizziness.
- Your prescriber will check your kidney function and blood potassium with blood tests after starting or changing treatment.
- A persistent dry cough is a recognised side effect; tell your prescriber if it becomes troublesome.
- Tell your prescriber if you might be pregnant, as ACE inhibitors are not suitable in pregnancy.
Weighing it up
Advantages & disadvantages of Captopril
Advantages
- Effective for high blood pressure and for heart failure with reduced pumping function.
- Long-established medicine with a well-understood safety profile.
- Helps protect the kidneys in some people, such as those with diabetes.
- Inexpensive and widely available.
Disadvantages
- Commonly causes a persistent dry cough.
- Can affect kidney function and raise blood potassium, so monitoring is needed.
- Usually needs to be taken more than once a day because it is short-acting.
- Must not be used in pregnancy, and rarely can cause swelling of the face or throat.
Practical use
Good to know
It is usually taken more than once a day because it is short-acting, and is often started low and built up, with a blood-pressure and blood-test check after starting and after increases. The first dose can cause a noticeable drop in blood pressure and dizziness, so it is introduced carefully, sometimes at bedtime. A dry, tickly cough is the most recognised nuisance effect of ACE inhibitors and, if troublesome, is usually solved by switching to an ARB. It must be stopped in pregnancy. Anti-inflammatory painkillers (NSAIDs), especially alongside a water tablet, can stress the kidneys.
Who should not take it / use with caution
- Women who are pregnant or planning pregnancy — ACE inhibitors are contraindicated in pregnancy and switched beforehand, as they can harm the developing baby.
- A history of angioedema (sudden swelling of the lips, tongue or throat), including from a previous ACE inhibitor — a reason never to take it again.
- Used with caution in significant kidney artery narrowing, low blood pressure, or a high blood potassium level.
Monitoring
- Blood pressure
- Kidney function and blood potassium before and after starting/increasing
- For cough or any swelling
Side effects
- A persistent dry cough (common and harmless, but can be annoying).
- Dizziness or light-headedness, especially on standing or after the first dose, which can be more pronounced as it acts quickly.
- A rise in blood potassium or a change in kidney function (watched with blood tests); a change in taste; rarely, angioedema — sudden swelling of the face or throat needs emergency care.
Key interactions
- NSAID painkillers (e.g. ibuprofen) can reduce its effect and stress the kidneys, especially alongside a diuretic (the "triple whammy").
- Potassium supplements, potassium-based salt substitutes and certain diuretics can push potassium too high.
- Care with other blood-pressure-lowering medicines, with ARBs, with lithium, and with some diabetes medicines.
Available as: Tablets (several strengths). A liquid can be specially prepared for people who cannot swallow tablets.
Answers
Captopril: frequently asked questions
Why do I take captopril more than once a day when other blood-pressure tablets are once daily?
Captopril is short-acting — it works and wears off quickly — so it usually has to be taken in divided doses through the day to keep blood pressure controlled. Newer ACE inhibitors last longer and are taken once a day, which is why they have largely replaced it for everyday use.
Why does captopril make me cough?
ACE inhibitors can cause a persistent dry, tickly cough in some people because of the way they affect natural body chemicals in the airways. It is harmless but can be annoying; if it bothers you, your prescriber can usually switch you to an ARB, which rarely causes a cough.
What is angioedema and why does it matter?
Angioedema is sudden swelling of the face, lips, tongue or throat. With an ACE inhibitor it is rare but a medical emergency, because throat swelling can affect breathing — call 999 if it happens. Anyone who has had it should never take an ACE inhibitor again.
Can I take captopril if I might become pregnant?
No — ACE inhibitors including captopril must be avoided in pregnancy because they can harm the developing baby. If you are planning a pregnancy, or think you may be pregnant, tell your prescriber promptly so you can be switched to a medicine that is safe in pregnancy.
What is the difference between captopril and Capoten?
They are the same medicine — captopril is the generic (active-ingredient) name and Capoten is the original brand name, used in both the UK and US. Generic captopril contains the identical active ingredient.
The wider class
About ACE inhibitors
Captopril belongs to the ace inhibitors class. For how the class as a whole works, its shared safety principles and monitoring, see the full guide.
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Authoritative sources
- BNF: Captopril.
- electronic Medicines Compendium (SmPC): Captopril (Capoten).
- NICE CKS: Captopril.
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