Why is it important to ask about exposure to toxins in a patient with suspected optic neuritis?

From the Guidelines

Es crucial preguntar sobre la exposición a toxinas en un paciente con sospecha de neuritis óptica porque ciertas toxinas pueden causar o mimetizar la neuritis óptica, afectando la diagnosis y las decisiones de tratamiento. Preguntar sobre la exposición a toxinas en un paciente con sospecha de neuritis óptica es importante porque ciertas toxinas pueden dañar el nervio óptico y producir síntomas similares a la neuritis óptica inflamatoria. Toxinas como el metanol, el glicol etilénico, el monóxido de carbono, el plomo y ciertos medicamentos (etambutol, isoniazida, amiodarona y clorafenicol) pueden dañar el nervio óptico y producir síntomas similares a la neuritis óptica inflamatoria 1. Además, las exposiciones ocupacionales a solventes, pesticidas y metales pesados pueden contribuir al daño del nervio óptico. Identificar una etiología tóxica es crucial porque el manejo difiere significativamente de las causas inflamatorias - el tratamiento se centra en eliminar el agente ofensivo y proporcionar cuidados de apoyo en lugar de administrar corticosteroides o terapia inmunomoduladora. Por lo tanto, es fundamental preguntar sobre la exposición a toxinas en un paciente con sospecha de neuritis óptica para evitar un tratamiento inadecuado, retrasar la recuperación o sufrir una pérdida de visión permanente que podría haberse prevenido mediante el reconocimiento y la eliminación temprana del agente tóxico 1. Algunos ejemplos de toxinas que pueden causar neuritis óptica incluyen:

• Medicamentos como el etambutol, que puede causar neuritis óptica y neuritis retrobulbar 1
• Toxinas como el metanol, que puede causar daño al nervio óptico y producir síntomas similares a la neuritis óptica inflamatoria
• Exposiciones ocupacionales a solventes, pesticidas y metales pesados, que pueden contribuir al daño del nervio óptico.

From the FDA Drug Label

ADVERSE REACTIONS ETHAMBUTOL HCl may produce decreases in visual acuity, including irreversible blindness, which appear to be due to optic neuritis. Optic neuropathy including optic neuritis or retrobulbar neuritis occurring in association with ethambutol therapy may be characterized by one or more of the following events: decreased visual acuity, scotoma, color blindness, and/or visual defect

The question of why it is important to ask about exposure to toxics in a patient with suspected optic neuritis is not directly addressed in the provided drug labels. Key points to consider in patients with suspected optic neuritis include:

• Optic neuritis may be caused by various factors, including certain medications like ethambutol.
• Toxic exposures can also cause optic neuritis, but this is not explicitly mentioned in the provided drug labels. The FDA drug label does not answer the question.

From the Research

Importance of Asking About Exposure to Toxics in Optic Neuritis

• Asking about exposure to toxics in a patient with suspected optic neuritis is crucial because toxic optic neuropathy (TON) can cause a similar clinical picture to optic neuritis 2
• TON is caused by damage to the optic nerve through different toxins, including drugs, metals, organic solvents, methanol, and carbon dioxide 2
• Certain medications, such as ethambutol, can cause optic neuropathy, and patients taking these medications should receive regular screening by an ophthalmologist 3
• Other neurological treatments, such as vigabatrin, isoniazid, and radiation therapy, can also adversely affect the eye and cause ocular complications 4

Potential Toxins and Optic Neuritis

• Drugs such as tuberculostatic drugs, antimicrobial agents, antiepileptic drugs, antiarrhythmic drugs, disulfiram, halogenated hydroquinolones, antimetabolites, tamoxifen, and phosphodiesterase type 5 inhibitors can cause optic neuropathy 2
• Exposure to these toxins can lead to optic neuropathy, which may be misdiagnosed as optic neuritis if a thorough history is not taken 2
• A detailed history of exposure to potential toxins is essential to diagnose and manage optic neuritis correctly 2, 3, 4

Clinical Implications

• Clinicians should be aware of the importance of patient and physician education, as well as timely and appropriate screening for optic neuropathy caused by toxins 3
• Regular screening by an ophthalmologist, including formal visual field testing, is recommended for patients taking medications that can cause optic neuropathy 3
• Visual evoked potentials and optical coherence tomography (OCT) may be helpful for screening, but more research is needed to clarify their clinical usefulness 3