A prodrug of ampicillin, a penicillin antibiotic
Bacampicillin
A penicillin antibiotic taken by mouth that the body turns into ampicillin to treat infections.
What is Bacampicillin?
Bacampicillin is an antibiotic taken by mouth that is a prodrug of ampicillin, meaning the body converts it into the active penicillin ampicillin after it is absorbed. It is used to treat bacterial infections. Being a penicillin, its most important safety concern is allergy, which can range from a rash to a severe reaction, so anyone with a penicillin allergy must avoid it. The most common everyday side effects are diarrhoea and rash. It is little used in routine UK practice today, with other penicillins more commonly chosen.
Education and reference only. This is a plain-language guide to Bacampicillin — 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
Bacampicillin is a penicillin antibiotic in the form of a prodrug: it is inactive as swallowed and is changed by the body into ampicillin, the active medicine, after being absorbed from the gut. This design was intended to improve how well the medicine is taken up compared with ampicillin alone. It is taken by mouth to treat various bacterial infections. As a penicillin, allergy is the key safety issue. It is not commonly used in current UK practice, where other penicillins are usually preferred.
How it works
Once swallowed and absorbed, bacampicillin is converted in the body into ampicillin, which is the substance that actually fights the infection. Ampicillin kills bacteria by interfering with the building of their cell wall, the protective layer they need to survive, so the bacteria break down and the infection clears. The prodrug approach was meant to help more of the medicine be absorbed from the gut before it is turned into active ampicillin. Because it acts on the bacterial cell wall, which human cells lack, it targets bacteria while generally sparing the body's own cells, though allergic reactions can still occur.
Company & origin
Originated / developed by: Generic.
A penicillin antibiotic taken by mouth that the body converts into ampicillin; designed for better absorption, it is little used in routine UK practice today.
Practical use
How to take Bacampicillin
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Take it by mouth exactly as prescribed, spacing the doses out evenly across the day.
- Do not take it if you have ever had an allergic reaction to penicillin; tell your prescriber about any allergies first.
- Complete the full course, even if you feel better, to clear the infection properly.
- Tell your prescriber if you develop a rash, and seek urgent help for swelling, wheeze or difficulty breathing.
- Report any diarrhoea, especially if it is severe or persistent.
Weighing it up
Advantages & disadvantages of Bacampicillin
Advantages
- Taken by mouth to treat a range of bacterial infections.
- Designed for better absorption than ampicillin, being converted to it in the body.
- Works by the well-understood penicillin action on the bacterial cell wall.
Disadvantages
- Can cause allergic reactions, including severe anaphylaxis, in people allergic to penicillin.
- Commonly causes diarrhoea and rash, and can lead to C. difficile infection.
- Little used in current UK practice, with other penicillins usually preferred.
Practical use
Good to know
As with any penicillin, the most important thing to know about bacampicillin is the risk of allergy: reactions range from a rash to a sudden, severe, life-threatening reaction (anaphylaxis), so anyone who has ever reacted to penicillin must not take it. The most common everyday side effects are diarrhoea and skin rash; some rashes are simple irritation, but any widespread rash, swelling or difficulty breathing needs urgent attention. Like other antibiotics, it can disturb the gut and occasionally cause C. difficile diarrhoea, so troublesome diarrhoea should be reported. It should be taken as a full course, even once you feel better, to clear the infection and help limit antibiotic resistance. In current UK practice it is little used, with other penicillins more commonly chosen, so it may be unfamiliar to many prescribers.
Who should not take it / use with caution
- People who are allergic to penicillins must not take it, as reactions can be severe.
- It is used with caution in people who have reacted to related antibiotics such as cephalosporins.
- It is used with care, and with dose review, in people with kidney problems, and on advice in pregnancy.
Monitoring
- Watching for allergic reactions, especially early in treatment.
- Reviewing the response to treatment and watching for diarrhoea or rash.
- Checking kidney function where needed, particularly in people with kidney problems.
Side effects
- Diarrhoea and other stomach upset, including, less commonly, C. difficile infection.
- Skin rash, ranging from mild irritation to allergic reactions.
- Rarely, severe allergic reactions (anaphylaxis) needing emergency treatment.
Key interactions
- The gout medicine probenecid can raise penicillin levels in the body.
- Penicillins may, rarely, affect how some other medicines work, so tell your prescriber everything you take.
- It may reduce how well some live vaccines, such as typhoid, work, so timing should be checked.
Available as: Tablets taken by mouth (an oral prodrug of ampicillin).
Answers
Bacampicillin: frequently asked questions
What is bacampicillin used for?
It is a penicillin antibiotic taken by mouth to treat bacterial infections; the body converts it into the active penicillin ampicillin after it is absorbed.
What does prodrug mean?
A prodrug is inactive as taken and is changed by the body into the active medicine; bacampicillin is converted into ampicillin after being absorbed.
Can I take it if I am allergic to penicillin?
No. Bacampicillin is a penicillin, so people allergic to penicillin must not take it because reactions can be severe and life-threatening.
What are the most common side effects?
Diarrhoea and skin rash are the most common; report any rash, and seek urgent help for swelling or difficulty breathing.
Do I need to finish the course?
Yes. Completing the full course as prescribed helps clear the infection properly and limits the development of antibiotic resistance.
The wider class
About Penicillin antibiotic (ampicillin prodrug)
Bacampicillin belongs to the penicillin antibiotic (ampicillin prodrug) class. For how the class as a whole works, its shared safety principles and monitoring, see the full guide.
Browse by body system
Authoritative sources
- BNF
- NICE CKS
Building a medicines information resource?
We create evidence-led, dose-free drug and formulary references for teams.