ETHAMBUTOL
DOSAGE
Adults: 15mg/kg once daily (oral); or for DOT supervised regimen: 30mg/kg three times per week. (Round the dose up or down to the closest whole number of tablets).
Obesity: It has been suggested that for markedly obese patients (consider for patients with BMI >30) should have an adjusted dose using ideal body weight:
Use ideal body weight plus 40% of the excess weight:
Children (1 month to 18 years): 15-25mg/kg once daily (oral); or for DOT supervised regimen: 30mg/kg three times per week. (Doses should be rounded down to facilitate administration of suitable volumes of liquid or an appropriate strength of tablet).
PREPARATIONS
Oral: 100mg, 400mg tablets
Voractiv® tablets (rifampicin 150mg, isoniazid 75mg, pyrazinamide 400mg, ethambutol 275mg).
Suspension (as a manufactured ‘special’ - unlicensed medicine).
An intravenous preparation may be available from specialist importers.
DRUG LEVEL MONITORING
Indications for monitoring:
Timing of sample:
ADVERSE EFFECTS
COMMON:
Endocrine: Hyperuricaemia.
Gastrointestinal: Nausea, vomiting.
SERIOUS:
Ophthalmic: Optic Neuritis (1-6%; greatest risk at doses >25mg/kg/day, or >2 months treatment), red/green colour blindness.
ADVERSE EFFECTS: MONITORING
Opthalmic:
Visual acuity and colour discrimination testing at baseline. In addition:
Routine tests as per generic MDR-TB treatment monitoring guidelines.
INTERACTONS
Isoniazid: Possible increased risk of optic neuropathy caused by ethambutol.
This information is not inclusive of all drug interactions. Please discuss with a pharmacist.
CONTRA-INDICATIONS & CAUTIONS
Contraindications:
Hypersensitivity: To ethambutol.
Ophthalmic: Optic neuritis and poor vision unless clinical judgement determines that it may be used.
Cautions:
Renal Disease: Reduce dose in severe renal impairment.
Young Children: Due to difficulty in testing eyesight and obtaining reports on symptomatic visual changes.
Elderly Patients: Due to the risks of ophthalmic adverse effects.
LABORATORY INFORMATION
Please find up to date information at www.assayfinder.com regarding individual providers of drug level monitoring tests. Click on the provider to discover contact details. Turnaround time varies depending on the test and whether it is run locally or sent to an external lab. By contacting laboratories in advance, turnaround time can significantly be reduced.
Sample Type: Serum.
Volume Required: 2 ml.
Sample Container: Plain (non SST).
Container Type: Any.
Availability: Office Hours.
Turnaround Time: 7 Days.
Adults: 15mg/kg once daily (oral); or for DOT supervised regimen: 30mg/kg three times per week. (Round the dose up or down to the closest whole number of tablets).
Obesity: It has been suggested that for markedly obese patients (consider for patients with BMI >30) should have an adjusted dose using ideal body weight:
Use ideal body weight plus 40% of the excess weight:
- Male ideal body weight (kg) = 50 + (2.3 x height in cm above (152.4/2.54))
- Female ideal body weight (kg) = 45.5 + (2.3 x height in cm above (152.4/2.54))
Children (1 month to 18 years): 15-25mg/kg once daily (oral); or for DOT supervised regimen: 30mg/kg three times per week. (Doses should be rounded down to facilitate administration of suitable volumes of liquid or an appropriate strength of tablet).
PREPARATIONS
Oral: 100mg, 400mg tablets
Voractiv® tablets (rifampicin 150mg, isoniazid 75mg, pyrazinamide 400mg, ethambutol 275mg).
Suspension (as a manufactured ‘special’ - unlicensed medicine).
An intravenous preparation may be available from specialist importers.
DRUG LEVEL MONITORING
Indications for monitoring:
- Known or suspected malabsorption.
- Renal impairment.
- Poor treatment response.
Timing of sample:
- 2 hours post dose.
- Repeat at 6 hours if suspect delayed.
- Drug levels need not be routinely measured.
ADVERSE EFFECTS
COMMON:
Endocrine: Hyperuricaemia.
Gastrointestinal: Nausea, vomiting.
SERIOUS:
Ophthalmic: Optic Neuritis (1-6%; greatest risk at doses >25mg/kg/day, or >2 months treatment), red/green colour blindness.
ADVERSE EFFECTS: MONITORING
Opthalmic:
Visual acuity and colour discrimination testing at baseline. In addition:
- Routine Monitoring: For doses of 15mg/kg: A symptom screen should be undertaken monthly. Any reported visual disturbance should result in prompt referral for formal ophthalmology assessment. If no complaints of visual disturbance, visual acuity and colour discrimination should be formally tested at least 6 monthly. The WHO and ATS recommend monthly testing after two months.
- Patients at higher risk of Opthalmic Toxicity (doses >15mg/kg OR children OR those with renal impairment): additional vigilance is advised and we recommend monthly visual acuity, colour discrimination testing and a symptom screen.
Routine tests as per generic MDR-TB treatment monitoring guidelines.
INTERACTONS
Isoniazid: Possible increased risk of optic neuropathy caused by ethambutol.
This information is not inclusive of all drug interactions. Please discuss with a pharmacist.
CONTRA-INDICATIONS & CAUTIONS
Contraindications:
Hypersensitivity: To ethambutol.
Ophthalmic: Optic neuritis and poor vision unless clinical judgement determines that it may be used.
Cautions:
Renal Disease: Reduce dose in severe renal impairment.
Young Children: Due to difficulty in testing eyesight and obtaining reports on symptomatic visual changes.
Elderly Patients: Due to the risks of ophthalmic adverse effects.
LABORATORY INFORMATION
Please find up to date information at www.assayfinder.com regarding individual providers of drug level monitoring tests. Click on the provider to discover contact details. Turnaround time varies depending on the test and whether it is run locally or sent to an external lab. By contacting laboratories in advance, turnaround time can significantly be reduced.
Sample Type: Serum.
Volume Required: 2 ml.
Sample Container: Plain (non SST).
Container Type: Any.
Availability: Office Hours.
Turnaround Time: 7 Days.