MYAMBUTOL

Route of administration:

Oral 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 15mg/kg, concomitant drugs being maintained at their recommended dosage levels.

For re-treatment:

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

For prophylaxis:

A single daily oral dose of 15mg/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 antituberculous drugs and appropriate dosage adjustments made.

Ethambutol should preferably be avoided in patients with renal impairment If used, where creatinine clearance is less than 30mL/minute, use 15–25 mg/kg (max. 5 g) 3 times a week and plasma ethambutol concentration should be monitored.

In this section, frequencies of undesirable effects are defined as follows:

Frequency: very common (>1/10); common (>1/100, <1/10); uncommon (>1/1,000, <1/100); rare (>1/10,000, <1/1,000), very rare (<1/10,000).

Blood & lymphatic system disorders:

Rare: Thrombocytopenia Very rare: Leucopenia, neutropenia Immune system disorders: Very rare: Hypersensitivity, anaphylactoid reactions, (see also Skin and subcutaneous tissue disorders) Metabolic & 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 & 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.

4) Musculoskeletal and connective tissue disorders: Very rare: Joint pains Renal & urinary disorders Very rare: Interstitial nephritis General disorders and administration site conditions: Very rare: Malaise, pyrexia Reporting of suspected adverse reactions Reporting suspected adverse reactions after authorisation of the medicinal product is important.

Renal function:

Toxic effects are more common if renal function is impaired.

Ocular toxicity:

Ethambutol may produce a unique type of visual impairment 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 25mg/kg/day for two months, and 15mg/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.

Routine ophthalmological examination for adults is not thereafter necessary, but patients should be informed the importance of reporting any change in vision. 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.

Hepatic impairment:

Liver function tests should be performed in patients who develop symptoms suggestive of hepatitis or who become generally unwell during treatment.

Skin and subcutaneous tissue disorders:

Ethambutol is contra-indicated in patients who are known to be hypersensitive to the drug. It is also contra-indicated in patients with known optic neuritis and poor vision unless clinical judgement determines that it may be used.