cycloserine: clinical use

Prescribing considerations

• Obtain cultures and establish susceptibility before treatment; assess susceptibility to other tuberculosis treatments being used.
• Review renal function because cycloserine is substantially excreted unchanged in urine and impaired clearance increases toxicity.
• Assess psychiatric history, alcohol use, neurological risk and porphyria.
• The therapeutic index is narrow; investigate emerging neuropsychiatric symptoms promptly.

Contraindications and cautions

• Hypersensitivity to cycloserine or an excipient.
• Epilepsy.
• Depression, severe anxiety or psychosis.
• Severe renal insufficiency.
• Alcohol abuse.
• Avoid in porphyria because clinical exacerbations have been reported.

Monitoring

• Monitor for seizures, tremor, drowsiness, confusion, psychosis, depression, speech disturbance and weakness.
• Check serum cycloserine concentrations where renal function is reduced or toxicity is suspected.
• Monitor renal function, liver function and haematology.
• Investigate anaemia, including possible folate or vitamin B12 deficiency.

Clinical pharmacology

Rapidly and almost completely absorbed orally, cycloserine distributes widely, including into cerebrospinal fluid, and is eliminated mainly through the kidneys. It inhibits cell-wall synthesis by competing with D-alanine.

Formulation and product differences

• The selected UK product is a red-and-grey hard gelatin capsule containing colourants that may cause allergic reactions.
• No alternative product formulation is represented by the selected SmPC.