Contents

Search

ethambutol (Myambutol)

Tradename: Myambutol. (ethambutol HCl) Indications: 1) treatment of tuberculosis in combination with other anti-tuberculous agents 2) used in combination with clarithromycin for disseminated Mycobacterium avium intracellulare Dosage: Tuberculosis: 1) 15-25 mg/kg PO QD 2) 50 mg/kg (max 2.5 g) twice a week MAI: 15 mg/kg/day as a single oral dose (max 1 g) Tabs: 100 & 400 mg. Dosage adjustment in renal failure: creatinine clearance dosage > 50-90 mL/min* every 24 hours 10-50 mL/min every 24-36 hours < 10 mL/min# every 48 hours * same dose for continuous arteriovenous hemofiltration # dose after hemodialysis Pharmacokinetics: 1) 80% is absorbed when taken orally 2) peak plasma levels 2-4 hours after oral ingestion 3) serum concentrations about 4 ug/mL 4) 1-5 ug/mL inhibitory for most strains of M. tuberculosis 5) distributes to most tissues & fluids 6) highest concentrations found in the lung, kidney, RBC & saliva 7) CSF levels low even in the presence of meningeal inflammation 8) elimination a) 80% in urine b) 1/2life if 4-6 hours (7-15 hours ESRD) Monitor: - BUN, serum creatinine every 6 months - complete blood count (CBC) every 6 months - liver function tests every 6 months - eye exams at baseline & periodically thereafter - patients on > 15 mg/kg/day should have monthly eye exams - monitor visual acuity & color vision [6] Adverse effects: 1) hyperuricemia & gout 2) abdominal pain 3) nausea/vomiting 4) rash 5) headache 6) confusion, disorientation 7) fever 8) peripheral neuritis 9) retrobulbar (optic) neuritis (most serious & frequent) a) blurred vision b) central scotoma c) red-green color blindness d) dose-related, < 1% for doses of 15 mg/kg e) frequency increased in patients with renal failure 10) fever 11) pruritus 12) abnormal liver function tests Drug interactions: - aluminum salts may decrease ethambutol absorption Mechanism of action: 1) inhibits bacterial RNA synthesis 2) impairs bacterial metabolism 3) bacteriostatic for M. tuberculosis & other replicating bacteria 4) only active when bacteria are actively dividing

Interactions

drug interactions

General

anti-tuberculous agent

Properties

MISC-INFO: elimination route LIVER KIDNEY 1/2life 4 HOURS elimination by hemodialysis - pregnancy-category B safety in lactation ?

Database Correlations

PUBCHEM correlations

References

  1. The Pharmacological Basis of Therapeutics, 9th ed. Gilman et al, eds. Permagon Press/McGraw Hill, 1996
  2. Am Thoracic Soc, Am J Respir Crit Care Med 149:1359, 1994
  3. Drug Information & Medication Formulary, Veterans Affairs, Central California Health Care System, 1st ed., Ravnan et al eds, 1998
  4. Kaiser Permanente Northern California Regional Drug Formulary, 1998
  5. deprecated reference
  6. Medical Knowledge Self Assessment Program (MKSAP) 17, American College of Physicians, Philadelphia 2015