ETHAMBUTOL

Posology The dosage of ethambutol must be adjusted according to the body weight of the patient Adults For primary treatment and prophylaxis Ethambutol should be administered in a single daily oral dose of 15 mg/kg, concomitant drugs being maintained at their recommended dosage levels.

For re-treatment For the first 60 days of treatment, a single daily oral dose of 25 mg/kg. Thereafter the dosage should be reduced to 15 mg/kg, concomitant drugs being maintained at their recommended dosage levels. Children For primary treatment and re-treatment For the first 60 days of treatment, a single daily oral dose of 25 mg/kg.

Thereafter the dosage should be reduced to 15 mg/kg, concomitant drugs being used at their recommended dosage levels. For prophylaxis A single daily oral dose of 15 mg/kg, concomitant drugs being used at their recommended dosage levels.

Elderly As for adults. However, patients with decreased renal function may need to have the dosage adjusted as determined by blood levels of ethambutol. In order to obtain maximum effect due to high serum levels, drug administration should be once daily.

Renal Impairment Renal function should be checked before treatment with antituberculosis medicinal products and appropriate dosage adjustments made. Ethambutol tablets should preferably be avoided in patients with renal impairment If used, where creatinine clearance is less than 30 mL/minute, use 15–25 mg/kg (max.

5 g) 3 times a week and plasma ethambutol concentration should be monitored. Method of administration Oral use only.

Frequencies are defined 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). Blood and lymphatic system disorders Rare: thrombocytopenia.

Very rare: leukopenia, neutropenia. Immune system disorders Very rare: hypersensitivity, anaphylactoid reactions (see also Skin and subcutaneous tissue disorders). Metabolism and nutrition disorders Uncommon: hyperuricaemia. Very rare: gout.

Nervous system disorders Rare: peripheral neuropathy, numbness, paraesthesia of the extremities. Very rare: headache, dizziness, disorientation. Psychiatric disorders Very rare: mental confusion, hallucinations. Eye disorders Uncommon: optic neuritis (decreased visual acuity, loss of vision, scotoma, colour blindness, visual disturbance, visual field defect, eye pain).

Respiratory, thoracic and mediastinal disorders Very rare: pneumonitis, pulmonary infiltrates, with or without eosinophilia. Gastrointestinal disorders Gastrointestinal disorders such as anorexia, nausea, vomiting, abdominal pain and diarrhoea have been noted in patients on multiple drug anti-tuberculosis therapy including ethambutol although not in test patients receiving ethambutol as sole therapy.

Hepatobiliary disorders Hepatic reactions with hepatitis, jaundice, abnormal liver function test values, and very rarely, hepatic failure, have been reported in patients treated with multiple drug therapy including ethambutol. Liver function tests should be performed in patients who develop symptoms suggestive of hepatitis or who become generally unwell during treatment.

Skin & subcutaneous tissue disorders Rare: rash, pruritus, urticaria. Very rare: photosensitive lichenoid eruptions, bullous dermatitis, Stevens Johnson syndrome (SJS), toxic epidermal necrolysis (TEN). 4). Renal and urinary disorders Very rare: interstitial nephritis.

Ocular toxicity Because this drug has a unique effect on the eye, which is generally reversible and which appears to be due to optic neuritis and to be related to dose and duration of treatment. Less than 1% of patients undergoing treatment with the higher dose regimen of 25 mg/kg/day for two months, and 15 mg/kg/day thereafter, have exhibited decrease in visual acuity.

It is recommended that patients undergo a full ophthalmic examination before starting treatment. This should include visual acuity, colour vision, perimetry and ophthalmoscopy. Any change may be unilateral or bilateral and hence both eyes should be tested individually.

Many physicians consider that routine ophthalmological examination for adults is not thereafter necessary, but patients should be informed the importance of reporting any change in vision. However, routine ophthalmological examinations may be considered desirable when treating young children.

Any negative effects on vision are generally reversible when administration of the drug is discontinued promptly and recovery of visual acuity has usually occurred over a period of weeks to months after the drug was discontinued. Patients have then received Ethambutol at lower dosages without toxicity.

In rare cases, recovery may be delayed for up to one year or more or the effects may be irreversible. Renal impairment Renal function should be checked before treatment with antituberculosis drugs and appropriate dosage adjustments made.

Ethambutol should preferably be avoided in patients with renal impairment, but if used the dose should be reduced and the plasma-drug concentration monitored. Toxic effects are more common if renal function is impaired. Hepatic impairment Liver function tests should be performed in patients who develop symptoms suggestive of hepatitis or who become generally unwell during treatment.

1. - a known optic neuritis and poor vision unless clinical judgement determines that it may be used.