Ethambutol
Ethambutol is a synthetic, bacteriostatic antimycobacterial agent used primarily as part of a multi-drug protocol (a "cocktail") to treat stubborn mycobacterial infections (such as *M. tuberculosis*, *M. bovis*, *M. genavense*, and *M. avium-intracellulare* complex) in dogs, cats, and birds. **Clinical Pearl:** Monotherapy is strictly avoided due to the rapid development of step-wise resistance. It is typically combined with drugs like rifampin, isoniazid, enrofloxacin, or macrolides. > **Important Public Health Note:** Treating mycobacterial infections in veterinary medicine is highly controversial due to the significant zoonotic potential and public health risks, particularly for immunocompromised individuals in the household.
Mecanismo: Ethambutol is active only against actively dividing mycobacteria. Mechanistically, it inhibits the enzyme **arabinosyl transferase** → disrupts the synthesis of arabinogalactan → prevents the incorporation of **mycolic acid** into the mycobacterial cell wall. This disruption increases cell wall permeability, which allows other antimycobacterial drugs (like rifampin or isoniazid) to penetrate the cell more effectively. It also interferes with RNA synthesis. It has no appreciable activity against other non-mycobacterial bacteria or fungi.
Dosificación por especie
- Treatment of feline tuberculosis (resistant cases) · 15 mg/kg PO once daily · PO · once daily · Not specified · Considered if resistance develops to initial therapy. Used in combination with rifampin and isoniazid.
- Treatment of M. avium infections in caged birds (Protocol 1) · 20 mg/kg PO q12h · PO · q12h · 6-12 months · Used with Ciprofloxacin/Enrofloxacin, Clofazimine, and Cycloserine.
- Treatment of M. avium infections in caged birds (Protocol 2) · 30 mg/kg PO once daily · PO · once daily · 6-12 months · Used with Clofazimine and Rifampin.
- Treatment of M. avium infections in caged birds (Protocol 3) · 30 mg/kg PO once daily · PO · once daily · 6-12 months · Used with Ciprofloxacin/Enrofloxacin and Rifampin/Rifabutin.
- Avian mycobacteriosis · 30-85 mg/kg PO once daily · PO · once daily · 9-12 months · Used with Rifabutin, Clarithromycin, and Enrofloxacin.
- Treatment of disseminated M. tuberculosis · 10-25 mg/kg PO once daily · PO · once daily · More than 9 months · Used in combination with rifampin (5-10 mg/kg PO q12-24h) and isoniazid (10-20 mg/kg PO once daily). May also add pyrazinamide (ineffective for M. bovis).
Las dosis son una referencia clínica para médicos veterinarios. Confirme siempre con la información vigente del producto y el paciente individual.
Vías de administración
Contraindicaciones
- Patients with a history of prior hypersensitivity reactions to ethambutol
Efectos adversos
- Optic neuritis (decreased visual acuity, usually reversible)
- CNS degenerative changes (with prolonged use)
- Myocardial toxicity (at high doses)
- Depigmentation of the tapetum lucidum
- Bacterial or fungal overgrowth (due to prolonged multi-drug antimicrobial therapy)
Interacciones farmacológicas
- Aluminum-containing antacids · Can reduce oral absorption of ethambutol; separate dosing by at least 4 hours if both are necessary
Monitoreo
- Clinical efficacy
- Visual function (periodic monitoring with long-term therapy)
- Liver function
- Renal function
- CBC
- Monitor for fungal or bacterial overgrowth infections
Sobredosis
Very limited veterinary information exists. In humans, acute overdoses of >10 grams have caused **optic neuritis**. Other adverse effects noted with human overdoses include CNS effects (confusion, visual hallucinations), abdominal pain, nausea, fever, and headache. Treatment is supportive.
La referencia de fármacos de VetSheet está destinada a médicos veterinarios como apoyo a la decisión clínica; no sustituye el juicio profesional ni la información vigente del fabricante.