An antibiotic used for drug-resistant tuberculosis
Cycloserine
A second-line antibiotic used as part of combination treatment for drug-resistant tuberculosis, known for affecting mood and the nervous system.
What is Cycloserine?
Cycloserine is a specialist antibiotic used as part of combination treatment for drug-resistant tuberculosis. Its most important feature is its effect on the brain and nervous system: it can cause depression, anxiety, confusion, and rarely psychosis or seizures, so mood and mental state are watched closely and it is avoided or used very carefully in people with epilepsy or serious mental-health problems. Vitamin B6 is often given alongside it to help reduce these effects. It is always used with other tuberculosis medicines, under specialist supervision, and the full course must be completed.
Education and reference only. This is a plain-language guide to Cycloserine — 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
Cycloserine is a second-line antibiotic, meaning it is used when the usual first-choice tuberculosis medicines are not suitable, particularly in drug-resistant tuberculosis. It is always used as part of a combination of medicines rather than on its own, to attack the bacteria in more than one way and prevent resistance. It is taken by mouth, usually over a long course. Because of its effects on the nervous system and mood, it is prescribed and closely supervised by a specialist tuberculosis team, and vitamin B6 is often added to help reduce these effects.
How it works
Cycloserine works against the bacteria that cause tuberculosis by interfering with the building of their cell walls, which they need to survive, so the bacteria are weakened and stopped from multiplying. It is used as part of a combination so the bacteria face several medicines at once, which makes resistance less likely. Because it can also act on the brain and nervous system, it may affect mood, thinking and, rarely, trigger seizures; this is why it is monitored carefully and why vitamin B6 is often given alongside it to help protect the nervous system.
Company & origin
Originated / developed by: Specialist manufacturer.
A specialist second-line antibiotic used in the UK as part of combination treatment for drug-resistant tuberculosis.
Practical use
How to take Cycloserine
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Take it by mouth as prescribed, as part of the full combination of tuberculosis medicines.
- Take any vitamin B6 you are given alongside it, as this helps reduce nerve-related effects.
- Report any low mood, anxiety, confusion, or thoughts of self-harm urgently.
- Avoid alcohol, as it increases the risk of seizures.
- Complete the whole course, even when you feel better, and do not stop without specialist advice.
Weighing it up
Advantages & disadvantages of Cycloserine
Advantages
- A useful second-line option for treating drug-resistant tuberculosis.
- Taken by mouth, which suits long courses of treatment.
- Works in a different way from first-line medicines, helping tackle resistant infection.
Disadvantages
- Can affect mood and the nervous system, causing depression, confusion, and rarely psychosis or seizures.
- Not suitable, or used very cautiously, in people with epilepsy or serious mental-health problems.
- Must always be used with other medicines and needs close monitoring.
Practical use
Good to know
The most important thing to understand about cycloserine is its effect on the brain and nervous system: it can cause low mood and depression, anxiety, irritability, confusion or difficulty concentrating, and less commonly more serious effects such as psychosis or seizures. Because of this, mood and mental state are checked regularly, any thoughts of self-harm or marked changes in mood or behaviour must be reported urgently, and it is avoided or used with great care in people with epilepsy or serious mental-health problems. Vitamin B6 is often given alongside it to help reduce nerve-related effects. Alcohol should be avoided as it increases the risk of seizures. It is always used as part of a combination, under specialist supervision, and the full course must be finished even when you feel better.
Who should not take it / use with caution
- People who have had a serious allergic reaction to cycloserine should not take it.
- It is avoided, or used with great care, in people with epilepsy, depression, severe anxiety or psychosis.
- It is used with care in people with serious kidney problems and in those who drink alcohol heavily.
Monitoring
- Regular checks of mood and mental state throughout treatment.
- Watching for confusion, psychosis or seizures.
- Checking how the infection responds and reviewing kidney function where needed.
Side effects
- Low mood, depression, anxiety, irritability or difficulty concentrating.
- Headache, dizziness or drowsiness.
- Less commonly but seriously, confusion, psychosis or seizures, which need urgent attention.
Key interactions
- Alcohol increases the risk of seizures and should be avoided.
- It can interact with some other medicines that affect the nervous system, so tell your team everything you take.
- Other tuberculosis medicines and vitamin B6 are used alongside it under specialist guidance.
Available as: Capsules taken by mouth.
Answers
Cycloserine: frequently asked questions
What is cycloserine used for?
It is a second-line antibiotic used as part of combination treatment for drug-resistant tuberculosis, when the usual first-choice medicines are not suitable.
Why does it affect my mood?
Cycloserine acts on the brain and nervous system, so it can cause low mood, anxiety, confusion and, rarely, more serious effects, which is why mental state is monitored.
Why am I given vitamin B6 with it?
Vitamin B6 is often given alongside cycloserine to help reduce its effects on the nerves and nervous system.
Can I drink alcohol with it?
No, alcohol should be avoided because it increases the risk of seizures while taking cycloserine.
Why must I take it with other medicines?
It is always used as part of a combination so the bacteria face several medicines at once, which reduces the chance of resistance.
The wider class
About Anti-tuberculosis antibiotic (second-line)
Cycloserine belongs to the anti-tuberculosis antibiotic (second-line) 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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