A first-generation cephalosporin antibiotic given by injection
Cefazolin
An injected cephalosporin antibiotic, commonly used to prevent infections during surgery.
What is Cefazolin?
Cefazolin is a first-generation cephalosporin antibiotic given by injection, used to treat certain bacterial infections and, very commonly, to prevent infection during surgery by being given around the time of an operation. The main safety points are allergy and cross-reactivity: people who are allergic to penicillin or other cephalosporins may also react to it, so any allergy history must be checked. Like all antibiotics, it can disturb the natural gut bacteria and lead to diarrhoea, including a more serious infection called Clostridioides difficile. It is given in hospital by injection into a vein or muscle.
Education and reference only. This is a plain-language guide to Cefazolin — 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
Cefazolin is an antibiotic belonging to the cephalosporin family, specifically a first-generation cephalosporin. It is given by injection, into a vein or a muscle, rather than by mouth, so it is used in hospital or clinical settings. It is used to treat certain bacterial infections, such as skin and soft-tissue infections, and it is very widely used to prevent infections during surgery, given just before an operation. As a cephalosporin, it is related to penicillin, which is important for people who have had reactions to penicillin antibiotics.
How it works
Cefazolin kills bacteria by interfering with their ability to build their cell walls. Bacteria need a strong, intact wall to survive, and cefazolin stops them from constructing it properly, so the bacteria break apart and die. This makes it effective against several common bacteria that cause skin and wound infections, which is why it is often chosen to prevent infection during surgery. Because it is broken down and cleared by the body fairly quickly, it is given as repeated injections to keep enough of the antibiotic present during and around an operation.
Company & origin
Originated / developed by: Various manufacturers.
A first-generation cephalosporin antibiotic given by injection, used in the UK and widely abroad, often to prevent infection during surgery.
Practical use
How to take Cefazolin
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Cefazolin is given by injection into a vein or muscle by healthcare staff, usually in hospital.
- Tell the team about any allergy to penicillin, cephalosporins or other antibiotics before it is given.
- Report any rash, swelling, wheeze or difficulty breathing during or after the injection straight away.
- Report severe or persistent diarrhoea during or after treatment, as it can be a sign of a gut infection.
- When used to prevent surgical infection, it is given around the time of the operation as the team directs.
Weighing it up
Advantages & disadvantages of Cefazolin
Advantages
- An effective antibiotic for certain infections and very widely used to prevent infection during surgery.
- Works against several common bacteria that cause skin and wound infections.
- Well established, with long experience of its use around operations.
Disadvantages
- Must be given by injection, so it is used in hospital or clinical settings rather than at home.
- People allergic to penicillin or other cephalosporins may also react to it.
- Like all antibiotics, it can cause diarrhoea, including the more serious Clostridioides difficile infection.
Practical use
Good to know
The most important safety issue with cefazolin is allergy. It is a cephalosporin, which is in the same broad family as penicillin, so people who have had an allergic reaction to penicillin or to other cephalosporins may also react to it; this is why your allergy history is always checked carefully before it is given, and a serious penicillin allergy may mean a different antibiotic is chosen. Like all antibiotics, it can upset the natural balance of bacteria in the gut, which can cause diarrhoea; sometimes this is due to a more serious infection called Clostridioides difficile, so any severe or persistent diarrhoea during or after treatment should be reported. It is used for the shortest effective time, and for surgery it is usually given just around the time of the operation. As it is given by injection in a clinical setting, the team monitors for any reactions when it is administered.
Who should not take it / use with caution
- People who have had a serious allergic reaction to cefazolin or other cephalosporins should not receive it.
- It is used with great caution, or avoided, in people who have had a severe allergic reaction to penicillin, because of cross-reactivity.
- It is used with care and the dose adjusted in people with kidney problems, under medical guidance.
Monitoring
- Watching for allergic reactions, especially when it is first given.
- Checking kidney function and adjusting the dose where needed.
- Watching for diarrhoea that could signal a gut infection.
Side effects
- Diarrhoea, feeling sick or stomach upset.
- Reactions where the injection is given, such as pain or irritation of the vein.
- Allergic reactions ranging from a rash to, rarely, a serious whole-body reaction, and rarely a more serious gut infection (Clostridioides difficile).
Key interactions
- It can interact with certain other medicines that affect the kidneys, so the team takes this into account.
- It may affect the results of some laboratory tests, which the staff allow for.
- Tell the team about all your medicines, including any blood thinners, so interactions can be checked.
Available as: A powder made up into a solution for injection into a vein or muscle.
Answers
Cefazolin: frequently asked questions
What is cefazolin used for?
It is a cephalosporin antibiotic given by injection to treat certain bacterial infections and, very commonly, to prevent infection during surgery.
Can I have it if I'm allergic to penicillin?
Cephalosporins like cefazolin are related to penicillin, so people with a penicillin allergy may also react; your allergy history is checked carefully, and a severe allergy may mean a different antibiotic is used.
How is it given?
It is given by injection into a vein or a muscle by healthcare staff, usually in hospital, rather than taken by mouth.
Why might it cause diarrhoea?
Like all antibiotics, it can disturb the natural balance of gut bacteria; severe or lasting diarrhoea should be reported, as it can signal a more serious gut infection.
Why is it used for operations?
It works well against the common bacteria that cause wound infections, so giving it around the time of surgery helps prevent infections from developing.
The wider class
About First-generation cephalosporin antibiotic
Cefazolin belongs to the first-generation cephalosporin 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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