The partner medicine combined with imipenem
Cilastatin
A partner medicine combined with the antibiotic imipenem to stop it being broken down in the kidney.
What is Cilastatin?
Cilastatin has no antibacterial effect by itself. It is combined with the antibiotic imipenem (a carbapenem) to stop imipenem being broken down by an enzyme in the kidney, so the antibiotic stays effective and the kidney is protected. The combination, imipenem-cilastatin, is a strong antibiotic given by drip in hospital for serious infections. The important cautions are those of the combination: a cross-allergy with penicillins (so a serious penicillin allergy matters), a risk of seizures (particularly at higher doses or with kidney problems), and the possibility of antibiotic-associated diarrhoea from C. difficile. It is used only under hospital supervision.
Education and reference only. This is a plain-language guide to Cilastatin — 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
Cilastatin is not an antibiotic and has no effect on bacteria on its own. Its role is to act as a partner to the antibiotic imipenem, a carbapenem, by protecting it from being destroyed in the kidney. The two are always given together as a single combination, imipenem-cilastatin, which is a powerful antibiotic used in hospital, by drip into a vein, to treat serious infections. Because cilastatin only ever comes paired with imipenem, the things to know about it are really the cautions of the combination as a whole. It is used under specialist hospital supervision.
How it works
The antibiotic imipenem kills bacteria, but on its own it is rapidly broken down by an enzyme in the kidney, which both weakens its effect and can be hard on the kidney. Cilastatin blocks that enzyme. By doing so, it stops imipenem being broken down, keeps the antibiotic at effective levels in the body, and helps protect the kidney. Cilastatin itself does nothing to the bacteria; its entire purpose is to make imipenem work properly. This is why the two are always given together as the combination imipenem-cilastatin.
Company & origin
Originated / developed by: Specialist manufacturer.
A medicine with no antibacterial effect of its own, combined with the antibiotic imipenem to protect it in the kidney; given as imipenem-cilastatin in hospital.
Practical use
How to take Cilastatin
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- It is given in hospital as a drip into a vein, always combined with imipenem, by your healthcare team.
- Tell the team if you have ever had a serious allergic reaction to penicillin or another antibiotic, as cross-allergy can occur.
- Tell the team if you have ever had seizures or have kidney problems, as these affect how the combination is used.
- Report any severe or watery diarrhoea, which can be a sign of a gut infection such as C. difficile.
- Attend any blood tests arranged, as kidney function is monitored during treatment.
Weighing it up
Advantages & disadvantages of Cilastatin
Advantages
- Allows the antibiotic imipenem to work effectively by stopping it being broken down in the kidney.
- Helps protect the kidney from the breakdown products of imipenem.
- Part of a powerful combination antibiotic used for serious hospital infections.
Disadvantages
- Has no antibacterial effect of its own and is only used combined with imipenem.
- The combination can cause seizures, particularly at higher doses or with kidney problems.
- Carries a risk of penicillin cross-allergy and of antibiotic-associated diarrhoea (C. difficile).
Practical use
Good to know
The key thing to understand is that cilastatin is purely a helper: it has no antibacterial action of its own and only ever comes combined with imipenem, so its cautions are those of the combination. Three matter most. First, there can be a cross-allergy between carbapenems and penicillins, so a history of serious penicillin allergy is important to mention. Second, the combination can lower the seizure threshold, meaning seizures are a recognised risk, particularly at higher doses, in people with kidney problems, or in those who already have a tendency to seizures. Third, like other broad antibiotics, it can disturb the gut bacteria and lead to antibiotic-associated diarrhoea, including Clostridioides difficile (C. difficile) infection, so any severe or persistent diarrhoea should be reported. The combination is given in hospital by drip with appropriate monitoring, including of kidney function.
Who should not take it / use with caution
- People who have had a serious allergic reaction to imipenem-cilastatin or to carbapenems should not receive it.
- It is used with great caution in people with a serious penicillin allergy, because of possible cross-allergy.
- It is used with caution in people with seizures or kidney problems, with doses adjusted accordingly.
Monitoring
- Monitoring kidney function, as doses may need adjusting in kidney problems.
- Watching for seizures, especially at higher doses or in people at risk.
- Watching for severe or persistent diarrhoea that could signal a C. difficile infection.
Side effects
- Nausea, vomiting or diarrhoea, which can include antibiotic-associated diarrhoea (C. difficile).
- Seizures, especially at higher doses, in people with kidney problems, or those prone to seizures.
- Allergic-type reactions, including, rarely, serious reactions needing urgent attention.
Key interactions
- The combination can interact with some other medicines, including certain ones that affect seizures, so tell the team everything you take.
- It can lower the level of the antiepileptic valproate, so this combination is generally avoided.
- Always tell the team about all your medicines, including those bought over the counter.
Available as: A powder made up into a solution and given as a drip into a vein, combined with imipenem.
Answers
Cilastatin: frequently asked questions
What does cilastatin do?
It has no antibacterial effect itself; it is combined with the antibiotic imipenem to stop imipenem being broken down by an enzyme in the kidney, keeping it effective and protecting the kidney.
Is cilastatin an antibiotic?
No. Cilastatin is not an antibiotic; it is a helper medicine that only ever comes combined with the antibiotic imipenem as imipenem-cilastatin.
Does penicillin allergy matter?
Yes. There can be a cross-allergy between carbapenems and penicillins, so a history of serious penicillin allergy is important to tell the team.
Can the combination cause seizures?
Yes, it can lower the seizure threshold, so seizures are a recognised risk, particularly at higher doses, with kidney problems, or in people prone to seizures.
Why might I get diarrhoea?
Like other broad antibiotics, the combination can disturb gut bacteria and cause antibiotic-associated diarrhoea, including C. difficile, so report any severe or persistent diarrhoea.
The wider class
About Enzyme inhibitor (combined with imipenem)
Cilastatin belongs to the enzyme inhibitor (combined with imipenem) 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.