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Cycloserine oral

Updated 2 Feb 2023 | Cycloserine


Oral formulations of cycloserine

Drugs List

  • cycloserine 250mg capsules
  • Therapeutic Indications


    Tuberculosis - resistant to first-line treatment
    Urinary tract infection

    Adjunctive treatment of active pulmonary and extra-pulmonary tuberculosis (including renal disease) where first line therapies have failed.

    Urinary tract infections caused by gram-positive and gram-negative bacteria when conventional therapy has failed.


    Before treatment is initiated, cultures should be taken and the susceptibility of the organism to cycloserine determined. For the treatment of tuberculosis, sensitivity to other antituberculosis agents should be demonstrated.


    250mg every 12 hours for two weeks, then 500mg to a maximum of 1g daily in divided doses, adjusted according to blood levels.


    10mg/kg/day, adjusted according to blood levels to achieve maximum response.

    The following alternative dosing schedule may be suitable:
    Tuberculosis resistant to first line drugs (use concurrently with other drugs):
    Children aged 12 to 18 years: 250mg twice daily for 2 weeks, increased up to maximum 500mg twice daily.
    Children aged 2 to 12 years: 5mg/kg (maximum 250mg) twice daily, increased up to 10mg/kg (maximum 500mg) twice daily.

    Patients with Renal Impairment

    Contraindicated in severe renal impairment.

    Blood levels should be determined at least weekly in patients with reduced renal function. A reduction in dose may be necessary. Adjust dose to keep blood levels below 30mg/l.

    The Renal Drug Handbook suggests the following doses in patients with renal impairment:
    Patients with GFR 10 to 50ml/minute
    250mg to 500mg every 24 hours. Monitor blood levels weekly.

    Patients with GFR less than 10ml/minute
    250mg to 500mg every 36 to 48 hours. Monitor blood levels weekly.


    Epileptic disorder
    Severe anxiety
    Severe renal impairment

    Precautions and Warnings

    Acute porphyria
    Mild renal impairment

    Advise patient drowsiness may affect ability to drive or operate machinery
    Consult national/regional policy on the use of anti-infectives
    Determine susceptibility to tuberculosis prior to treatment
    Take cultures for sensitivity testing before and regularly during treatment
    Monitor blood concentration - should not exceed 30mg/litre
    Monitor drug blood levels weekly in renal impairment or if high dose
    Monitor for occurrence of anaemia
    Monitor renal, hepatic and haematological parameters
    Discontinue or reduce dose if allergic dermatitis occurs
    Discontinue or reduce dose if CNS toxicity occurs
    Advise patient to avoid alcohol during treatment

    Toxicity is usually associated with blood levels greater than 30 mg/l. The therapeutic index for cycloserine is low.

    Monitor blood levels and reduce dose for patients with renal dysfunction, for individuals receiving doses above 500 mg daily and in patients with signs and symptoms of toxicity. Adjust dose to keep blood levels below 30 mg/l.

    Discontinue or reduce dose if allergic dermatitis or symptoms of CNS toxicity (e.g. convulsions, psychosis, somnolence, depression, confusion, hyperreflexia) occur. Patients on more than 500 mg daily should be closely monitored for these symptoms. Anticonvulsant drugs or sedatives may be effective in controlling symptoms of CNS toxicity. The value of pyridoxine in preventing CNS toxicity from cycloserine has not been proven.

    Determine susceptibility of organism to cycloserine and concurrent therapy in tuberculosis prior to treatment.

    Patients taking cycloserine with anti-tuberculosis therapy may develop vitamin B12 deficiency, folic acid deficiency, megaloblastic anaemia and sideroblastic anaemia. If this occurs investigations and treatment is recommended.

    Cycloserine has been associated with clinical exacerbations of porphyria.

    Pregnancy and Lactation


    Use cycloserine with caution in pregnancy.

    Briggs suggests cycloserine should not be withheld because of pregnancy but notes that limited data prevents a complete risk assessment. Schaefer suggests that single case reports do not prove a high teratogenic risk. The manufacturer suggests cycloserine should only be given in pregnancy if clearly needed.

    It is unknown whether cycloserine can cause foetal harm or affect reproductive capability. Concentrations in foetal blood approach those found in the serum. Limited data (3 pregnancies) on exposure to cycloserine during first trimester do not suggest adverse foetal effects.

    Animal studies in rats revealed no teratogenic effects given in doses up to 100 mg/kg daily.

    The use of all medication in pregnancy should be avoided whenever possible; particularly in the first trimester. Non-drug treatments should also be considered. When essential, a medication with the best safety record over time should be chosen, employing the lowest effective dose for the shortest possible time. Polypharmacy should be avoided. Teratogens taken in the pre-embryonic period, often quoted as lasting until 14 to 17 days post-conception, are believed to have an all-or-nothing effect. Where drugs have a short half-life, and when the date of conception is certain, this may allow women to be reassured where drug exposure has occurred within this time frame. Further advice may be available from the UK National Teratology Information Service (NTIS) and through ToxBase, available via password on the internet ( ) or if this is unavailable at the backup site ( ).


    Use cycloserine with caution in breastfeeding.

    Schaefer suggests a decision whether to limit breastfeeding during cycloserine therapy should be taken. Hale suggests because of the potentially significant levels of cycloserine in human milk, breastfeeding should be withheld for 24 hours. The Drugs and Lactation Database (LactMed) suggests if use is required, it is not reason to discontinue breastfeeding but that exclusively breastfed infants should be monitored, possibly with measurement of serum levels. The manufacturer suggests to take a decision of discontinuing cycloserine or discontinuing breastfeeding, taking into account the benefit of therapy to the patient.

    Cycloserine is excreted into breast milk. Concentrations of cycloserine in the mother's milk approach those found in the serum.

    No adverse effects were observed in breastfed infants whose mothers were receiving cycloserine.

    Neonates, infants born prematurely, those with low birth weight, those with an unstable gastrointestinal function or who have serious illnesses may require special consideration. For any infant, if a drug is prescribed to the nursing mother, it should be at the lowest practical dose and for the shortest time. When drug administration is unavoidable and breastfeeding is to continue, minimisation of exposure of the infant to the drug may sometimes be achieved by timing the maternal doses to just after a feeding episode. Infants exposed to drugs via breast milk should be monitored for unusual signs or symptoms. Interactions between the drug received by the infant from the mother's milk and medication prescribed for the infant should also be considered, for example, when the drug given to the infant may prevent metabolism of the drug received via breast milk.
    Specialist advice is available from the UK Drugs in Lactation Advisory Service at

    Side Effects

    Allergic reaction
    Congestive cardiac failure
    Increase in aminotransferase level
    Megaloblastic anaemia
    Memory loss
    Personality change
    Suicidal tendencies


    It is strongly recommended that the UK National Poisons Information Service be consulted on cases of suspected or actual overdose where there is doubt over the degree of risk or about appropriate management.

    The following number will direct the caller to the relevant local centre (0844) 892 0111

    Information may be obtained if you have access to ToxBase the primary clinical toxicology database of the National Poisons Information Service. This is available via password on the internet ( ) or if this is unavailable at the backup site ( ).

    Further Information

    Last Full Review Date: December 2016

    Reference Sources

    Drugs in Pregnancy and Lactation: A Reference Guide to Fetal and Neonatal Risk, 10th edition (2015) ed. Briggs, G., Freeman, R. Wolters Kluwer Health, Philadelphia.

    Drugs During Pregnancy and Lactation: Treatment Options and Risk Assessment, 3rd edition (2015) ed. Schaefer, C., Peters, P. and Miller, R. Elsevier, London.

    Medications and Mothers' Milk, Sixteenth Edition (2014) Hale, T and Rowe, H, Hale Publishing, Plano, Texas.

    Summary of Product Characteristics: Cycloserine 250 mg capsules. King Pharmaceuticals Ltd. Revised November 2015.

    NICE - Evidence Services
    Available at:
    Last accessed: 23 June 2017.

    US National Library of Medicine. Toxicology Data Network. Drugs and Lactation Database (LactMed).
    Available at:
    Cycloserine. Last revised: September 7, 2013.
    Last accessed: December 9, 2016.

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