How does ethambutol affect the eyes?
Ethambutol-induced optic neuropathy (EON) is a well-known complication that results from the use of ethambutol. The ocular manifestations of EON include painless loss of central vision and cecocentral scotomas in the visual field.
How does ethambutol cause optic neuropathy?
While the exact mechanism of the neurotoxic effect of EMB on the optic nerve is unknown, it is believed that the metal chelating effects of this drug may be responsible. One theory is that the chelation of copper disrupts oxidative phosphorylation, as there is less copper available in human mitochondria.
What is ethambutol toxicity?
Ethambutol is an antimicrobial agent used frequently to treat tuberculosis. The most commonly recognized toxic effect of ethambutol is optic neuropathy, which generally is considered uncommon and reversible in medical literature.
Is ethambutol ocular toxicity reversible?
Delayed onset ocular ethambutol toxicity is usually considered to be reversible following prompt withdrawal of the drug.
Does ethambutol cause blindness?
The most important complication of ethambutol therapy is retrobulbar neuritis manifest by impaired visual acuity, color blindness and restricted visual fields. Except in patients with pre-existing ophthalmic disease, optic neuritis is extremely rare when ethambutol is used at standard doses (15 mg/kg).
What is Ocular toxicity?
Ocular toxicity is characterized by one or more adverse changes that affect the structure or function of the eye following application of a substance, drug, or device directly on or in the eye or an alternate site in the body distant to the eye.
Can ethambutol cause blindness?
What is the mechanism of action of ethambutol?
Mechanism of action Ethambutol is bacteriostatic against actively growing TB bacilli. It works by obstructing the formation of cell wall. Mycolic acids attach to the 5′-hydroxyl groups of D-arabinose residues of arabinogalactan and form mycolyl-arabinogalactan-peptidoglycan complex in the cell wall.
How do you manage ethambutol toxicity?
Once ethambutol-induced ocular toxicity is recognised, the drug should be immediately stopped and the patient referred to an ophthalmologist for further evaluation. Presently, therapy discontinuation is the only effective management strategy that can stop the progression of vision loss and allow recovery of vision.
Does rifampin cause eye problems?
Rifampicin causes visual acuity, which appear to be due to optic neuritis. This effect may be related to dose and duration of treatment. This effect is generally reversible when administration of the drug is discontinued promptly[21].