A carbapenem antibiotic given with cilastatin (imipenem-cilastatin)
Imipenem
A powerful hospital antibiotic, given with cilastatin into a vein, used for serious infections.
What is Imipenem?
Imipenem is a powerful antibiotic in the carbapenem group, used in hospital to treat serious infections. It is always combined with another medicine called cilastatin (the combination is imipenem-cilastatin), which protects imipenem so it can work properly in the body, and it is given as a drip into a vein. Its most important safety concern is a risk of seizures (fits), which is higher in people with kidney problems or at high doses. It can cause allergic reactions and can react in people allergic to penicillin, can cause antibiotic-related diarrhoea (including C. difficile), and it lowers the levels of the epilepsy medicine valproate.
Education and reference only. This is a plain-language guide to Imipenem — 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
Imipenem is a broad-acting antibiotic belonging to a group called the carbapenems, which are kept for serious infections, often those caused by bacteria that other antibiotics cannot tackle. It is always given together with cilastatin, a partner medicine that stops imipenem being broken down too quickly in the kidneys, so the combination is known as imipenem-cilastatin. It is a hospital medicine given as a drip into a vein, prescribed and supervised by hospital teams, often with advice from microbiology specialists.
How it works
Imipenem kills bacteria by stopping them building their cell walls, which they need to survive; without a proper wall, the bacteria break apart and die. It works against a very wide range of bacteria, which is why it is reserved for serious or difficult infections. Cilastatin does not kill bacteria itself; instead it blocks an enzyme in the kidneys that would otherwise break imipenem down, allowing imipenem to reach effective levels and work properly. This is why the two are always given together as imipenem-cilastatin.
Company & origin
Originated / developed by: Specialist manufacturers.
A powerful hospital antibiotic used in the UK for serious infections, always combined with cilastatin and given into a vein.
Practical use
How to take Imipenem
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- It is given as a drip into a vein by hospital staff, always combined with cilastatin.
- Tell the team about any allergy to penicillin or other antibiotics before it is given.
- Report any twitching, confusion or a fit straight away, as carbapenems can rarely trigger seizures.
- Tell the team about severe or watery diarrhoea, as this can occasionally signal a serious bowel infection.
- Make sure the team knows if you take sodium valproate, as imipenem can make it stop working.
Weighing it up
Advantages & disadvantages of Imipenem
Advantages
- A powerful antibiotic effective against a very wide range of bacteria.
- Useful for serious infections, including some that other antibiotics cannot treat.
- Cilastatin protects it so it can reach effective levels and work properly.
Disadvantages
- Carries a risk of seizures, especially with kidney problems or high doses.
- Can cause allergic reactions and may react in people allergic to penicillin.
- Can cause antibiotic-related diarrhoea, including C. difficile, and lowers the epilepsy medicine valproate.
Practical use
Good to know
The dominant safety concern with imipenem is the risk of seizures (fits): carbapenems can lower the seizure threshold, and the risk is higher in people with kidney impairment, those given high doses, or those who already have a brain or seizure condition, so the dose is adjusted carefully for kidney function. Because it is related to penicillins, people with a serious penicillin allergy can sometimes react to it, so allergy history matters. Like other broad antibiotics, it can disturb the gut bacteria and cause diarrhoea, including the more serious infection C. difficile, so any severe or persistent diarrhoea should be reported. An important interaction is with sodium valproate (an epilepsy medicine): imipenem lowers valproate levels and can lead to loss of seizure control, so this combination is generally avoided.
Who should not take it / use with caution
- People who have had a serious allergic reaction to imipenem or other carbapenems should not use it.
- It is used with great caution in people with a serious penicillin allergy, because of possible cross-reaction.
- It is used with care, and the dose adjusted, in people with kidney problems or a history of seizures.
- It is generally avoided in people taking sodium valproate, as it can make valproate stop working.
Monitoring
- Checking kidney function so the dose can be adjusted to reduce the risk of seizures.
- Watching for allergic reactions, neurological symptoms and severe diarrhoea.
- Reviewing the response to treatment and the choice of antibiotic with the infection team.
Side effects
- Nausea, vomiting or diarrhoea.
- Reactions where the drip goes in, such as pain or inflammation of the vein.
- Allergic reactions, including rash and, rarely, serious reactions.
- Rarely but seriously, seizures, or severe diarrhoea from a C. difficile bowel infection, which need urgent attention.
Key interactions
- Sodium valproate: imipenem lowers its level and can lead to loss of seizure control, so the combination is generally avoided.
- Other medicines that lower the seizure threshold may add to the risk of fits.
- Tell the team about all your medicines, including the gout medicine probenecid, which can affect its handling.
Available as: A powder made up into a solution given as a drip into a vein.
Answers
Imipenem: frequently asked questions
What is imipenem used for?
It is a powerful hospital antibiotic used to treat serious infections, including some caused by bacteria that other antibiotics cannot tackle.
Why is it given with cilastatin?
Cilastatin protects imipenem from being broken down too quickly in the kidneys, so it can reach effective levels and work properly; the two are always given together.
Why is there a risk of seizures?
Carbapenems can lower the seizure threshold, and the risk is higher in people with kidney problems, on high doses, or with a brain or seizure condition, so the dose is adjusted carefully.
Can I have it if I am allergic to penicillin?
Imipenem is related to penicillins, so people with a serious penicillin allergy can sometimes react to it; always tell the team about any antibiotic allergy.
Why does it matter if I take valproate?
Imipenem lowers the level of the epilepsy medicine sodium valproate, which can lead to loss of seizure control, so the combination is generally avoided.
The wider class
About Carbapenem antibiotic
Imipenem belongs to the carbapenem antibiotic 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
- NICE CKS
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