Cycloserine

Mechanism-of-action class: Enzyme Inhibitors.

• Cycloserine is indicated in the treatment of active pulmonary and extrapulmonary tuberculosis (including renal disease) when the causative organisms are susceptible to this drug and when treatment with the primary medications (streptomycin, isoniazid, rifampin, and ethambutol) has proved inadequate. Like all antituberculosis drugs, cycloserine should be administered in conjunction with other effective chemotherapy and not as the sole therapeutic agent.ICD-10: A15.9

• Administration is contraindicated in patients with any of the following: • Hypersensitivity to cycloserine • Epilepsy • Depression, severe anxiety, or psychosis • Severe renal insufficiency • Excessive concurrent use of alcohocontraindicated

Cycloserine is effective orally and is currently administered only by this route. The usual dosage is 500 mg to 1 g daily in divided doses monitored by blood levels. 1 The initial adult dosage most frequently given is 250 mg twice daily at 12-hour intervals for the first 2 weeks. A daily dosage of 1 g should not be exceeded.

Administration of cycloserine should be discontinued or the dosage reduced if the patient develops allergic dermatitis or symptoms of CNS toxicity, such as convulsions, psychosis, somnolence, depression, confusion, hyperreflexia, headache, tremor, vertigo paresis, or dysarthria. The toxicity of cycloserine is closely related to excessive blood levels (above 30 mcg/mL), as determined by high dosage or inadequate renal clearance. The ratio of toxic dose to effective dose in tuberculosis is small. The risk of convulsions is increased in chronic alcoholics. Patients should be monitored by hematologic, renal excretion, blood level, and liver function studies.

Most adverse reactions occurring during therapy with cycloserine involve the nervous system or are manifestations of drug hypersensitivity. The following side effects have been observed in patients receiving cycloserine: Nervous system symptoms (which appear to be related to higher dosages of the drug, i.e., more than 500 mg daily) • Convulsions • Drowsiness and somnolence • Headache • Tremor • Dysarthria • Vertigo • Confusion and disorientation with loss of memory • Psychoses, possibly with suicidal tendencies • Character changes • Hyperirritability • Aggression • Paresis • Hyperreflexia • Paresthesia • Major & minor (localized) clonic seizures • Coma Cardiovascular: Sudden development of congestive heart failure in patients receiving 1 to 1.5 g of cycloserine daily has been reported. Allergy (apparently not related to dosage) Skin rash Miscellaneous: Elevated serum transaminase, especially in patients with preexisting liver disease To report SUSPECTED ADVERSE REACTIONS, contact Cerovene, Inc. at 1-833-304-9569 or FDA at 1‑800-FDA-1088 or www.fda.gov/medwatch.

Signs and Symptoms: Acute toxicity from cycloserine can occur if more than 1 g is ingested by an adult. Chronic toxicity from cycloserine is dose related and can occur if more than 500 mg is administered daily. The central nervous system is the most common organ system involved with toxicity. Toxic effects may include headache, vertigo, confusion, drowsiness, hyperirritability, paresthesias, dysarthria, psychosis paresis, convulsions, and coma. Treatment: In adults, many of the neurotoxic effects of cycloserine can be both treated and prevented with the administration of 200 to 300 mg of pyridoxine daily. Hemodialysis has been shown to remove cycloserine from the bloodstream. This procedure should be reserved for patients with life threatening toxicity that is unresponsive to less invasive therapy.

• Jun 29, 1964ANDAANDA060593Sanaluz

1. 1Electrocardiogram Qt Prolonged29013%
2. 2Off Label Use27112%
3. 3Neuropathy Peripheral22410%
4. 4Anaemia2189.8%
5. 5Vomiting1727.7%
6. 6Nausea1496.7%
7. 7Drug Resistance1175.3%
8. 8Hepatotoxicity1115.0%
9. 9Tuberculosis964.3%
10. 10Death853.8%
11. 11Dyspnoea833.7%
12. 12Asthenia793.5%
13. 13Product Use In Unapproved Indication773.5%
14. 14Drug Reaction With Eosinophilia And Systemic Symptoms723.2%
15. 15Intentional Product Use Issue703.1%

Recent PubMed references pinned to Cycloserine as a MeSH major topic. Citations link to pubmed.ncbi.nlm.nih.gov.

• Mechanism-Based Polypharmacy as a Repurposing Strategy: The Case of D-Cycloserine and Lurasidone.
  Clinical and translational science · 2026 · Franzen AD, Svendsen JS, Kline CJ, et al.
  PMID 42251640DOI 10.1111/cts.70624
• A novel sequential ketamine and D-cycloserine/lurasidone therapy for bipolar depression with acute suicidal ideation.
  Expert opinion on investigational drugs · 2026 · Takahashi M, Shelton RC
  PMID 42166622DOI 10.1080/13543784.2026.2674645
• L-Cycloserine, not d-Cycloserine, inhibits IscS-mediated iron-sulfur cluster biosynthesis in Escherichia coli.
  International journal of antimicrobial agents · 2026 · Zhang L, Li Y, Bao Y, et al.
  PMID 41759600DOI 10.1016/j.ijantimicag.2026.107761
• Towards model-informed precision dosing of clofazimine, moxifloxacin, and terizidone/cycloserine in the treatment of drug-resistant tuberculosis: An external model evaluation study.
  Tuberculosis (Edinburgh, Scotland) · 2026 · Behrens E, Köhler N, Münchow M, et al.
  PMID 41687300DOI 10.1016/j.tube.2026.102744
• A systematic review of pharmacological effects on human aversive memory.
  Neuroscience and biobehavioral reviews · 2026 · Xia Y, Quednow BB, Bach DR, et al.
  PMID 41513054DOI 10.1016/j.neubiorev.2026.106548
• Enhancing the Efficacy of Exposure Therapy: Translation of Pharmacological Augmentation of Fear Extinction.
  Annual review of clinical psychology · 2026 · Smits JAJ, Kredlow MA, Monfils MH, et al.
  PMID 41349549DOI 10.1146/annurev-clinpsy-061324-071811
• Exploring effects of chronic d-cycloserine administration on expression of GluN2 subunits and tripartite synaptic transmission in thalamocortical pathway.
  British journal of pharmacology · 2026 · Okada M, Okubo R, Yamamoto N, et al.
  PMID 41314791DOI 10.1111/bph.70262
• Cycloserine-induced neuropsychiatric toxicity in multidrug-resistant tuberculosis: association with peak plasma concentration.
  Microbiology spectrum · 2025 · Cheng J, Li J, Zheng R, et al.
  PMID 41190861DOI 10.1128/spectrum.01437-25

The 10 most recently updated of 151 ClinicalTrials.gov registrations naming Cycloserine as an intervention. Registration is not evidence of efficacy or safety — reference crosswalk only.

• A Pilot Trial of One-Day Accelerated TMS and D-cycloserine in Suicidal Patients With Borderline Personality Disorder
  Recruiting · Phase 1 · Phase 2 · Interventional · 20 enrolled · Mclean Hospital
  NCT07460947updated 2026-06-04
• A Randomized, Double-Blind Controlled Comparison of NRX-101 vs. Placebo for Adults Being Treated With Robotic Transcranial Magnetic Stimulation for Treatment Resistant Depression: The MIND1 Trial
  Not yet recruiting · Phase 2 · Phase 3 · Interventional · 400 enrolled · NeuroRx, Inc.
  NCT07227103updated 2026-06-04
• Study of Radiation Exposure and Bilateral Breast Cancer
  Active not recruiting · Observational · 1,699 enrolled · Memorial Sloan Kettering Cancer Center
  NCT00903591updated 2026-06-03
• Synaptic Mechanisms of Intermittent Theta Burst Stimulation for Major Depressive Disorder
  Not yet recruiting · Phase 1 · Phase 2 · Interventional · 100 enrolled · Mclean Hospital
  NCT07593222updated 2026-05-18
• Synaptic Mechanisms of Continuous Theta Burst Stimulation in Depression
  Recruiting · Early phase 1 · Interventional · 80 enrolled · Mclean Hospital
  NCT07560878updated 2026-05-13
• D-cycloserine for the Treatment of Chronic, Refractory Low Back Pain
  Terminated · Phase 2 · Interventional · 203 enrolled · Northwestern University
  NCT03535688updated 2026-05-04
• D-Cycloserine for Serine Palmitoyltransferase Inhibition
  Completed · Phase 4 · Interventional · 1 enrolled · Massachusetts General Hospital
  NCT07542548updated 2026-04-21
• Optimized, Neuroplasticity-Enhanced-Depression (ONE-D) Transcranial Magnetic Stimulation (TMS) Treatment for Female Athletes With Co-morbid Depression and Concussion
  Not yet recruiting · Phase 2 · Phase 3 · Interventional · 35 enrolled · University of Florida
  NCT07507214updated 2026-04-02
• AIH for Spinal Cord Repair
  Terminated · Early phase 1 · Interventional · 50 enrolled · VA Office of Research and Development
  NCT03780829updated 2026-02-27
• Assisting Smokers to Switch to an e-Cigarette by Accelerating Learning of Adaptive Habits Using D-cycloserine
  Completed · Phase 2 · Interventional · 25 enrolled · Rose Research Center, LLC
  NCT05994703updated 2026-01-20

Frequently asked questions

How does Cycloserine work?

Mechanism-of-action class: Enzyme Inhibitors.

What is Cycloserine used for?

According to FDA labeling, Cycloserine carries indications including: Cycloserine is indicated in the treatment of active pulmonary and extrapulmonary tuberculosis (including renal disease) when the causative organisms are susceptible to this drug and when treatment with the primary medications (streptomycin, isoniazid, rifampin, and ethambutol) has proved inadequate. Like all antituberculosis drugs, cycloserine should be administered in conjunction with other effective chemotherapy and not as the sole therapeutic agent.. This is a reference summary of labeled uses, not medical advice or a treatment recommendation.

What class of drug is Cycloserine?

Cycloserine is classified as Antibiotics, Enzyme Inhibitors, Decreased Cell Wall Synthesis & Repair.

What are the brand names for Cycloserine?

Cycloserine is marketed under brand names including Seromycin.

What are the contraindications for Cycloserine?

Cycloserine labeling lists contraindications including: Administration is contraindicated in patients with any of the following: • Hypersensitivity to cycloserine • Epilepsy • Depression, severe anxiety, or psychosis • Severe renal insufficiency • Excessive concurrent use of alcoho. Always consult the full prescribing information and a clinician.