Cycloserine

1 medicine

Cycloserine is a second-line antibiotic for multidrug-resistant tuberculosis. It can cause serious central nervous system effects, including seizures, psychosis, and suicidal depression, especially at higher doses.

Seromycin

Cycloserine

250mg

Seromycin is a antibiotics medication containing Cycloserine, available as 250mg capsules.

from $4.56 / capsule View

Key facts

  • Cycloserine is a second-line antibiotic used with other drugs to treat multidrug-resistant tuberculosis (MDR-TB) when standard TB medicines have failed or cannot be used.
  • It's taken as capsules, usually once or twice daily, always alongside several other anti-TB drugs, for many months as part of a supervised regimen.
  • Cycloserine can cause serious central nervous system effects: seizures, psychosis, and depression with suicidal thoughts. Risk rises with higher doses, kidney impairment, alcohol use, or a personal history of seizures or mental illness.
  • Seek urgent care for a seizure, new confusion, hallucinations, or thoughts of self-harm.

What cycloserine treats

Cycloserine treats tuberculosis caused by bacteria resistant to first-line drugs, including multidrug-resistant TB, TB that has spread to the lining of the brain, and TB affecting bones or joints. It is always used in combination with other anti-TB medicines, never alone, because resistance develops quickly to a single drug.

How cycloserine works

Cycloserine mimics D-alanine, a building block Mycobacterium tuberculosis needs to construct its cell wall. The bacteria take it up in place of the real building block, which blocks the enzymes that assemble the wall. Without a properly formed wall, the bacteria can no longer survive or divide.

Before you take it

  • Tell your prescriber about any history of seizures, depression, or other mental health conditions; cycloserine can worsen these and may need extra monitoring or a different drug.
  • Kidney impairment slows clearance of cycloserine, letting levels build up; your dose and blood levels are checked more closely if your kidneys are affected.
  • Avoid alcohol. It lowers the seizure threshold and adds to cycloserine's nervous-system side effects.
  • Pyridoxine (vitamin B6) is often given alongside cycloserine, since it can reduce nerve-related side effects.

Side effects

Common effects include nausea, headache, dizziness, and fatigue, usually mild and easing over the first weeks.

Stop and seek urgent medical care for:

  • A seizure.
  • Severe confusion, hallucinations, or unusual behaviour.
  • Thoughts of self-harm or suicide, or a sudden worsening of mood.
  • A severe allergic reaction: hives, facial swelling, or difficulty breathing.

Safety essentials

  • Cycloserine carries a well-documented risk of serious central nervous system toxicity: seizures, psychosis, and suicidal depression, that rises with dose and with kidney impairment; blood level monitoring is recommended above 500 mg a day or if kidney function is reduced.
  • Tell your prescriber immediately about mood changes, unusual thoughts, or new confusion; these can be early signs that need a dose change.
  • Never drink alcohol while taking cycloserine, and tell your prescriber about any other seizure-lowering medicines you take.

This page is educational and does not replace advice from a doctor or pharmacist who knows your health history.