Optic neuritis ethambutol

Optic neuritis (a decrease in visual acuity and changes in color perception), which appears to be related to the dose given and die duration of treatment, has occurred in some patients receiving ethambutol. Usually, tiiis adverse reaction disappears when the drug is discontinued. Other adverse reactions are dermatitis, pruritus, anaphylactoid reactions (unusual or exaggerated allergic reactions), joint pain, anorexia, nausea, and vomiting. 

Hypersensitivity to ethambutol known optic neuritis, unless clinical judgment determines that it may be used. 

Ethambutol (Myambutel) [Antitubercular Agent] Uses Pulm TB other mycobacterial Infxns, MAC Action i RNA synth Dose Adults Feds >12 y. 15-25 mg/kg/d PO single dose X in renal impair, take w/ food, avoid antacids Caution [B, +] Contra Unconscious pts, optic neuritis Disp Tabs SE HA, hyperuricemia, acute gout, abd pain, T LFTs, optic neuritis, GI upset Interactions T Neurotox W/ neurotoxic drugs X effects W/ A1 salts EMS May affect glucose (hypoglycemia) may cause vision problems OD Sxs unknown activated charcoal may be effective symptomatic and supportive... 

Ethambutol (child 6 years or older) 15 mg/kg orally, for 2 months (child 6 years or older) 45 mg/kg orally, for 2 months (child 6 years or older) 30 mg/kg oraUy, for 2 months Optic neuritis Not recommended for children too young to be monitored for changes in vision... 

A. Ethambutol is associated with retrobulbar neuritis, resulting in loss of central vision and impaired red-green discrimination. Ethionamide (B) is an analogue of isonicotinic acid and is associated with GI intolerance and peripheral neuropathy, but not the optic neuritis or color vision discrimination problems. Aminosalicylic acid (C) can cause GI irritation and bleeding problems, so caution is required in peptic ulcer patients. It has no neurological side effects. Rifampin (D) is associated with red-orange discoloration of saliva, tears, and urine but not the color vision problems. Isoniazid (E) is associated with peripheral neuritis in chronic alcoholics and malnourished individuals and requires pyridoxine supplements. It is not associated with optic neuritis. 

Optic neuritis (more common with high-dosage or long-term ethambutol therapy), peripheral neuritis, thrombocytopenia, and an anaphylactoid reaction occur rarely. 

Ethambutol suppresses the growth of isoniazid- and streptomycin-resistant tubercle bacilli. The most important but not common side effects are optic neuritis, decreased visual acuity, and inability to perceive the color green. 

Ethambutol [e THAM byoo tole] is bacteriostatic and specific for most strains of M- tuberculosis and M- kansasii. Resistance is not a serious problem if the drug is employed with other antituberculous agents. Ethambutol can be used in combination with pyrazinamide, isoniazid, and rifampin to treat tuberculosis. Absorbed on oral administration, ethambutol is well distributed throughout the body. Penetration into the central nervous system (CNS) is therapeutically adequate in tuberculous meningitis. Both parent drug and metabolites are excreted by glomerular filtration and tubular secretion. The most important adverse effect is optic neuritis, which results in... 

The optic nerve is of interest here because some drugs are toxic to this tissue.The antibiotics chloramphenicol, ethambutol, streptomycin, and sulfonamides can cause optic neuritis. Vitamin A, especially in large doses, can result in papilledema. Digitalis can cause retrobulbar neuritis (see Chapter 35). 

Modified from Garrett CR. Optic neuritis in a patient on ethambutol and isoniazid evaluated by visual evoked potentials case report. Mil Med 1985 150 43-46. 

Nervous system. Tardive dyskinesias occur with neuroleptics polyneuritis with metronidazole optic neuritis with ethambutol. 

Side effects caused by isoniazid, rifampin, pyrazinamide, and ethambutol are common and can include hepatotoxic-ity, peripheral neuropathy, optic neuritis, and Gl side effects. All four agents can potentially be hepatotoxic, but this side effect is most frequently associated with isoniazid and rifampin. Peripheral neuropathy is most commonly associated with isoniazid, whereas optic neuritis is associated with ethambutol. The metabolism of isoniazid is genetically predetermined. Patients of Scandinavian, European, and African descent metabolize isoniazid slower (slow acetylators) and are therefore more predisposed to hepatotoxicity and peripheral neuropathy due to isoniazid. Fast acetylators include people of Asian or American Indian descent and are less predisposed to these adverse effects. 

Ethambutol The (S,S)-form of ethambutol is a tuberculostatic agent the (i ,i )-form causes optical neuritis that can lead to blindness... 

The use of ethambutol in the chemotherapy of tuberculosis is described in the following text. The most important side effect is optic neuritis, resulting in decreased visual acuity and loss of ability to differentiate red from green. The incidence of this reaction is proportional to the dose of ethambutol and is observed in 15% of patients receiving 50 mg/kg day, in 5% of patients receiving 25 mg/kg per day, and fewer than 1% of patients receiving daily doses of 15 mg/kg (the recommended dose for treatment of tuberculosis). The intensity of the visual difficulty is related to the duration of therapy after the decreased visual acuity first becomes apparent, and may be unilateral or bilateral. Tests of visual acuity and red-green discrimination prior to the start of therapy and periodically thereafter are thus... 

Ethambutol >15mg/kg/day Optic neuritis, red/green colorblindness, peripheral neuropathy. 

The mean serum levels of a 300-mg dose of isoniazid were not signifieant-ly ehanged in 10 patients with tubereulosis when they were given a single 20-mg/kg dose of ethambutol. The possible effeets ofeoneurrent use over a period of time were not studied. However, there is some evidence that the optic neuropathy caused by ethambutol may be increased by isoniazid, and any effects resolve more slowly after the use of isoniazid. One group of authors recommends that both ethambutol and isoniazid should be stopped immediately if severe optic neuritis occurs. They further recommend that isoniazid should be stopped if less severe optic neuritis does not improve within 6 weeks after stopping ethambutol. ... 

Amongst the cases reported by Ok-cu (39 ), however, were 4 of optic neuritis, all of whom improved after ethambutol was withdrawn. 

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