|1. TYPE OF DRUG -ETHAMBUTOL|
|Ethambutol eliminates certain bacteria that cause tuberculosis (TB).
|2. INDICATIONS (USE) -ETHAMBUTOL|
|For use, as an adjunct, in the treatment of tuberculosis.
|3. MECHANISM OF ACTION (MOA) -ETHAMBUTOL|
|Ethambutol inhibits arabinosyl transferases which is involved in cell wall biosynthesis. By inhibiting this enzyme, the bacterial cell wall complex production is inhibited. This leads to an increase in cell wall permeability.
|4. ROUTES OF ADMINISTRATION -ETHAMBUTOL|
|5. ONSET OF EFFECT OR ACTION -ETHAMBUTOL|
|It may take several days for the symptoms to improve.
|6. DOSAGE (DOSING INFORMATION) -ETHAMBUTOL|
Primary treatment of pulmonary and extrapulmonary tuberculosis
Adult: As hydrochloride: Initial 8 wk: 15 mg/kg/day or 30 mg/kg thrice wkly given with isoniazid, rifampicin and pyrazinamide. For patients with history of antimycobacterial therapy: Initial doses: 25 mg/kg/day for 60 days, thereafter reduce to 15 mg/kg/day.
Child: For treatment of drug-resistant tuberculosis: 15-25 mg/kg daily or 50 mg/kg twice wkly. For congenitally acquired tuberculosis: Neonates: 15 mg/kg once daily and ≥1 mth: 15 mg/kg once daily or 30 mg/kg 3 times wkly for 2 mth initial treatment phase.
Renal impairment: Dose reduction may be required.
|7. HALF LIFE (DURATION OF ACTION) -ETHAMBUTOL|
|In patients with normal renal function, 3 to 4 hours. In patients with impaired renal function, up to 8 hours.
|8. ADVERSE EFFECTS OR SIDE EFFECTS -ETHAMBUTOL|
|Retrobulbar neuritis with a reduction in visual acuity, constriction of visual field, central or peripheral scotoma and green-red colour blindness. Retinal haemorrhage (rare); reduced renal clearance of urates (acute gout); GI disturbances eg, nausea, vomiting, abdominal pain, anorexia; rash, headache, dizziness, confusion, hallucinations, malaise, jaundice; thrombocytopenia; pulmonary infiltrates.
|9. CONTRAINDICATIONS -ETHAMBUTOL|
|Hypersensitivity; optic neuritis. Lactation
|10. DRUG INTERACTIONS -ETHAMBUTOL|
|Absorption delayed or reduced by aluminum hydroxide. Synergistic effect with other antitubercular agents.
|11. EXCRETION -ETHAMBUTOL|
|During the 24-hour period following oral administration of ethambutol hydrochloride approximately 50 percent of the initial dose is excreted unchanged in the urine, while an additional 8 to 15 percent appears in the form of metabolites. From 20 to 22 percent of the initial dose is excreted in the feces as unchanged drug.