CYCLOSERINE

Posology Adults:

The usual dosage is 500 mg to 1 g daily in divided doses, monitored by blood level determinations. The initial adult dosage most frequently given is 250 mg twice daily at 12- hour intervals for the first two weeks. A daily dosage of 1g should not be exceeded.

The elderly:

As adults but reduce dosage if renal function is impaired. Paediatric population The usual starting dose is 10 mg/ kg/ day, then adjusted according to blood levels obtained and therapeutic response. Method of administration For oral administration.

The undesirable effects reported with Cycloserine during clinical trials and post-marketing surveillance are shown in the table below. They are listed by System-Organ Class (SOC) and in order of frequency, using the following convention: very common (≥1/10); common (≥1/100 to <1/10); uncommon (≥1/1,000 to <1/100); rare (≥1/10,000 to <1/1,000); very rare (<1/10,000); not known (cannot be estimated from the available data).

5 g daily dose of Cycloserine) * Especially in patients with pre-existing liver disease. Reporting of suspected adverse reactions Reporting suspected adverse reactions after authorisation of the medicinal product is important. It allows continues monitoring of the benefit/risk balance of the medicinal product.

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Administration of cyclosenne should be discontinued or the dosage reduced if the patient develops allergic dermatitis or symptoms of central nervous system toxicity such as convulsions, psychosis, somnolence, depression, confusion, hyper-refiexia, headache, tremor, vertigo, paresis or dysarthria.

Toxicity is usually associated with blood levels of greater than 30mg/l, which may be the result of high dosage or inadequate renal clearance. The therapeutic index for this drug is low. The risk of convulsions is increased in chronic alcoholics (see ‘Precautions’ section).

Patients should be monitored by haematological, renal excretion, blood level and liver function studies. Before treatment with cycloserine is begun, cultures should be taken and the susceptibility of the organism to the drug should be established.

In tuberculous infections, sensitivity to the other anti-tuberculous agents in the regimen should also be demonstrated. Blood levels should be determined at least weekly for patients having reduced renal function, for individuals receiving a daily dosage of more than 500mg, and for those showing signs and symptoms suggestive of toxicity.

The dosage should be adjusted to keep the blood level below 30mg/l. Anticonvulsant drugs or sedatives may be effective in controlling symptoms of central nervous system toxicity, such as convulsions, anxiety or tremor. Patients receiving more than 500mg of cycloserine daily should be closely observed for such symptoms.

The value of pyridoxine in preventing CNS toxicity from cycloserine has not been proven. Administration of cycloserine and other anti-tuberculous drugs has been associated in a few instances with vitamin B12 and/or folic acid deficiency, megaloblastic anaemia and sideroblastic anaemia.

If evidence of anaemia develops during treatment, appropriate investigations and treatment should be carried out. Cycloserine has been associated with clinical exacerbations of porphyria and is not recommended in porphyric patients.

1 Cycloserine is contra-indicated in the presence of any of the following conditions: epilepsy; depression, severe anxiety or psychosis; severe renal insufficiency; alcohol abuse.