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Toxins in Neuro-Ophthalmology
Published in Vivek Lal, A Clinical Approach to Neuro-Ophthalmic Disorders, 2023
Optical coherence tomography (OCT) can detect the toxicity of ethambutol even before the changes apparent on fundus examination and has been used as an additional objective test to monitor patients on ethambutol [9]. High-risk patients are those who are older, have chronic kidney disease and taking high dose. The visual toxicity of ethambutol can be monitored by visual-evoked potentials (VEPs). In a study on 14 patients receiving ethambutol, Pattern shift visual-evoked potential (PSVEP) was abnormal in five patients; however, the symptoms were present in one patient only [12].
An immigrant from Thailand with a cough
Published in Tim French, Terry Wardle, The Problem-Based Learning Workbook, 2022
Some pretreatment precautions and tests are recommended because of the risk of side-effects from antituberculosis therapy: ethambutol has a toxic effect on the eye. Although this is rare, visual acuity should be assessed using a Snellen chart before commencing treatment, and reassessed during the course of treatment to detect any deterioration as early as possiblean uncommon side-effect of ethambutol is acute renal failure. Urea and electrolytes must be checked before starting treatment. It is also advisable to monitor renal function during antituberculosis treatmentall antituberculosis drugs have the potential to cause hepatitis. Thus, patients should have liver function tests before treatment, and regularly throughout treatment.
Tuberculosis in Childhood and Pregnancy
Published in Lloyd N. Friedman, Martin Dedicoat, Peter D. O. Davies, Clinical Tuberculosis, 2020
Lindsay H. Cameron, Jeffrey R. Starke
Pyrazinamide has been used extensively in children; hepatitis and complications of hyperuricemia are exceedingly rare events. Ethambutol is also safe in children and is widely used in the first-line regimen for the treatment of childhood tuberculosis. Optic toxicity is rare in children, and formal ophthalmologic evaluation of asymptomatic children is not necessary. Ethionamide is well tolerated in children and is considered a first-line therapy for tuberculous meningitis. Children may experience nausea and vomiting, but less frequently than adults. Baseline thyroid function testing followed by monitoring 6-month intervals is recommended for children receiving long-term ethionamide therapy.
The Genetics of Ethambutol-Induced Optic Neuropathy: A Narrative Review
Published in Neuro-Ophthalmology, 2022
Prabhjit Kaur, Sofia Singh, Kirandeep Kaur, Karthik Vinay Mahesh, Basavaraj Tigari, Vineet Sehgal, Aastha Takkar, Sahil Mehta, Ramandeep Singh, Samir Malhotra
Tuberculosis (TB) is a global health problem with the major brunt of disease occurring in developing countries. With the advent of anti-tubercular therapy (ATT), the incidence of TB has reduced (1.3% average reduction per year since 2002).1,2 Although the thrice a week directly observed treatment short-course (DOTS) was an effective strategy in India the introduction of daily fixed drug combinations (FDCs) have led to improved treatment success.3 As per the modification of guidelines by the World Health Organisation (WHO), in some countries, such as India, Botswana, Canada, Ghana and European countries,4 the treatment courses of ethambutol have been prolonged.5 While rifampicin (R), isoniazid (H), pyrazinamide (Z) and ethambutol (E) are recommended daily in the intensive phase (IP), combination treatment with HRE has been advised in the continuation phase for most of the subcategories of TB (pulmonary, central nervous system and skeletal TB).4 Anecdotal evidence of increased incidence of ocular side effects of ethambutol is accumulating.6
Ethambutol-induced optic neuropathy: Functional and structural changes in the retina and optic nerve
Published in Seminars in Ophthalmology, 2022
Sagnik Sen, Sohini Mandal, Mousumi Banerjee, Ranjitha Gk, Abhyuday Saxena, Swati Phuljhele Aalok, Rohit Saxena
Patients who are planned to undergo EMB treatment should be explained in detail about the possibility of vision loss, the need for periodic screening, and follow up with an ophthalmologist including the vigilance to identify any visual disturbance early. Physicians should be sensitized about the risk of ethambutol toxicity and the high incidence of subclinical damage. Screening protocol for subclinical EON has, however, not yet been established. Baseline examination should include visual acuity, color vision, visual field testing, and dilated fundus examination.102 Careful administration of ethambutol dose is important, and any patient who is on higher dosage or prolonged duration of the drug should be assessed regularly using these parameters irrespective of absence of visual complains. Although the Physicians’ Desk Reference (PDR), in United States, recommends monthly ophthalmic examinations for patients taking EMB doses >15 mg/kg/day, it may not be practically feasible for patients in developing countries.46 Once the visual loss due to optic neuropathy is identified, the patient should be referred back to the treating physician to decide regarding the continuation or cessation of therapy based upon the risk–benefit ratio.
Chapter 5: Treatment of tuberculosis disease
Published in Canadian Journal of Respiratory, Critical Care, and Sleep Medicine, 2022
James C. Johnston, Ryan Cooper, Dick Menzies
Ethambutol (EMB) inhibits growth of M. tuberculosis. It is the least effective of the first-line drugs for bactericidal activity (Objective 1) and prevention of relapse (Objective 3), but it is a well-tolerated companion drug that effectively prevents drug resistance (Objective 2). EMB is added to the initial phase of therapy until DST is available. In people with TB that is fully susceptible to all first-line drugs, EMB can be discontinued. If DST is not available and drug-resistant disease is not suspected, EMB should be continued throughout treatment. EMB is associated with optic neuropathy, which presents with decreased visual acuity and/or colour vision changes.16 Rare adverse effects include rash, hematologic effects, GI upset and neurologic effects.9