Drug reference

Cycloserine

Antibacterial · Antituberculosis

AntibacterialAntituberculosisATC null

CDSCO approvedSchedule H

EXCRETION

—

not curated

INTERACTIONS

5 major

SEVERE in our sources

PREGNANCY

Manufacturer advises use only if potential beneﬁt outweighs risk—crosses the placenta.

FDA category + note

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Mechanism

Cycloserine acts as a structural analog of D-alanine, interfering with bacterial cell wall synthesis. It inhibits two critical enzymes: alanine racemase, which converts L-alanine to D-alanine, and D-alanyl-D-alanine ligase. This dual inhibition prevents the incorporation of D-alanine into the peptidoglycan pentapeptide, thereby disrupting cell wall integrity and leading to bacterial demise, particularly in Mycobacterium tuberculosis.

Indications

Tuberculosis resistant to first-line drugs, in combination with other drugsmultidrug-resistant tuberculosisResistant TB (especially MDR cases)MAC infectionGram-positive bacteria infectionsE. coli infectionsChlamydia infections

Dosing

Adult: Initially 250 mg every 12 hours for 2 weeks, then increased if necessary up to 500 mg every 12 hours by mouth, dose to be increased according to blood concentration and response
Renal adjustment: Increase interval between doses if creatinine clearance less than 50 mL/minute. Monitor blood-cycloserine concentration if creatinine clearance less than 50 mL/minute; blood concentration should not exceed 30 mg/litre.
Max dose: 1000 mg/day

Pharmacokinetics

Half-life

9 h

Bioavailability

Almost completely absorbed orally

Metabolism

About 1/3 of a dose is metabolized

Excretion

Urine (50% unchanged in first 12 h, 70% active form over 24 h)

Contraindications

Alcohol dependence
depression
epilepsy
psychotic states
severe anxiety
depression (use with caution)
Patients with a history of mental illness or seizures

Side effects

Common

Behaviour abnormalconfusiondrowsinessdysarthriaheadachehyperirritabilitymemory lossneurological effectsparaesthesiaparesisrashreﬂexes increasedtremorvertigosomnolencesevere psychosisseizuressuicidal ideationsCNS toxicity - headacheSleepinessSlurring of speechAltered behaviourDepressionFall in BP

Serious