ethambutol (e-tham-byoo-tole) Etibi, Myambutol

 Indications

Active tuberculosis or other mycobacterial diseases

(with at least one other drug).

Action

Inhibits the growth of mycobacteria. Therapeutic

Effects: Tuberculostatic effect against susceptible organisms.

Pharmacokinetics

Absorption: Rapidly and well absorbed (80%) from

the GI tract.

Distribution: Widely distributed; crosses bloodbrain

barrier in small amounts; crosses placenta and

enters breast milk.

Protein Binding: 20–30%.

Metabolism and Excretion: 50% metabolized by

the liver, 50% eliminated unchanged by the kidneys.

Half-life: 3.3 hr (increased in renal or hepatic impairment).

TIME/ACTION PROFILE (blood levels)

ROUTE ONSET PEAK DURATION

PO rapid 2–4 hr 24 hr

Contraindications/Precautions

Contraindicated in: Hypersensitivity; Optic neuritis.

Use Cautiously in: Renal and severe hepatic impairment

(dosage reduction required); OB: Although

safety not established, ethambutol has been used with

isoniazid in pregnant women without fetal adverse effects;

Lactation: Usually compatible with breast feeding

(AAP).

Adverse Reactions/Side Effects

CNS: confusion, dizziness, hallucinations, headache,

malaise. EENT: optic neuritis. GI: HEPATITIS, abdominal

pain, anorexia, nausea, vomiting.Metab: hyperuricemia.

MS: joint pain. Neuro: peripheral neuritis.

Resp: pulmonary infiltrates. Misc: anaphylactoid reactions,

fever.

Interactions

Drug-Drug: Neurotoxicity may beqwith other neurotoxic

agents. Aluminum hydroxide may decrease

absorption (space doses 4 hr apart).

Route/Dosage

PO (Adults and Children 13 yr): 15–25 mg/kg/

day (maximum 2.5 g/day) or 50 mg/kg (up to 2.5 g)

twice weekly or 25–30 mg/kg (up to 2.5 g) 3 times

weekly.

PO (Children 1 mo—13 yr): HIV negative—15–

20 mg/kg/day once daily (maximum: 1 g/day) or 50

mg/kg/dose twice weekly (maximum: 2.5 g/dose); HIVexposed/-

infected—15–25 mg/kg/day once daily

(maximum: 2.5 g/day); MAC, secondary prophylaxis,

or treatment in HIV-exposed/-infected—15–25 mg/

kg/day once daily (maximum: 2.5 g/day) with clarithromycin

(or azithromycin) with or without rifabutin;

Nontuberculous mycobacterial infection—15–25

mg/kg/day once daily (maximum: 2.5 g/day).

Availability (generic available)

Tablets: 100 mg, 400 mg.