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Nutritional Optic Neuropathy
Published in Vivek Lal, A Clinical Approach to Neuro-Ophthalmic Disorders, 2023
William Sultan, Giulia Amore, Uchenna Francis Nwako, Stacey Aquino Cohitmingao, Samuel Asanad, Alfredo Sadun
Medication use should be carefully assessed since several antibiotics may cause toxic neuropathy with different mechanisms. The most frequent causes of optic nerve damage are two anti-tuberculosis agents, ethambutol and isoniazid, interfering respectively with mitochondrial oxidative phosphorylation and protein synthesis. Amiodarone toxicity, an antiarrhythmic, is characterized by a prolonged optic disc swelling. Other molecules are the immunosuppressants tacrolimus and cyclosporine.
Microorganisms
Published in John C Watkinson, Raymond W Clarke, Louise Jayne Clark, Adam J Donne, R James A England, Hisham M Mehanna, Gerald William McGarry, Sean Carrie, Basic Sciences Endocrine Surgery Rhinology, 2018
Ursula Altmeyer, Penelope Redding, Nitish Khanna
Three agents form the mainstay of anti-tuberculous therapy: rifampicin, ethambutol and isoniazid, and most anti-tuberculous regimens will include some or all of these agents. Other agents may include aminoglycosides, such as amikacin or kanamycin.
Mycobacterium tuberculosis – The Organism
Published in Peter D O Davies, Stephen B Gordon, Geraint Davies, Clinical Tuberculosis, 2014
This agent inhibits the enzyme arabinosyl transferase, which is involved in the synthesis of the major cell wall polysaccharide arabinogalactan. Acquisition of resistance is a multi step mutational process involving several genes in the embA, embB and embC gene cluster (principally embB), which code for this enzyme. A rather bizarre finding is that mutations in codon 306 of the embB gene not only impart resistance to ethambutol but predispose the bacterial cell to develop resistance to a range of anti-tuberculosis agents, thereby generating multidrug resistant strains [76]. There is only a weak association between resistance to isoniazid and ethambutol, although isoniazid-resistant strains with one particular mutation in the katG gene are more likely to acquire high-level resistance to ethambutol [77].
The effects of lutein on optic nerve injury induced by ethambutol and isoniazid: an experimental study
Published in Cutaneous and Ocular Toxicology, 2019
Yucel Karakurt, Halis Süleyman, Ferda Keskin Cimen, Gamze Tasli, Turgay Ucak, Erel Icel, Nezahat Kurt
Ethambutol and isoniazid are the two major agents in tuberculosis treatment. Ethambutol induced optic neuropathy is an important issue since it may be irreversible. Although isoniazid induced visual disturbances were reported to be reversible, the concomitant affects of these two agents when used together is still not elucidated exactly. In a large study on 4803 newly diagnosed tuberculosis cases the incidence of ethambutol-related optic neuropathy was reported as 1.29%; and in only half of those cases ethambutol discontinuation revealed a significant visual improvement13. Today the only way of treatment in anti-tuberculosis agent induced optic neuropathy is the discontinuation of the agent. In that aspect, prevention of anti-tuberculosis treatment associated toxic optic neuropathy gains more importance.
Current research toward optimizing dosing of first-line antituberculosis treatment
Published in Expert Review of Anti-infective Therapy, 2019
Helen McIlleron, Maxwell T Chirehwa
Many antituberculosis drugs exhibit wide pharmacokinetic variability in patient cohorts [1–13]. Studies in patients with drug-susceptible tuberculosis (DS-TB) on a standard regimen of rifampin and isoniazid for 6 months with pyrazinamide and ethambutol for the first 2 months, suggest that such variability is clinically important. Specifically, patients with relatively low systemic exposures to rifampin and pyrazinamide have worse treatment outcomes [4,6], while rifampin, isoniazid and pyrazinamide exposures are related to the decline in bacterial load in the sputum during the weeks following initiation of treatment [6,8,14–18]. For ethambutol and isoniazid, as well as second-line drugs for drug-resistant tuberculosis (DR-TB), such as linezolid, cycloserine, moxifloxacin, aminoglycosides, and capreomycin toxicity, are dose-related. Dose optimization should therefore aim to limit the number of patients with lower or higher than optimal drug exposures.
Infectious spondylodiscitis: 5-year analysis of a tertiary hospital in Portugal
Published in Infectious Diseases, 2018
Ana Ponciano, Gonçalo Cruz, Conceição Ventura, Eduardo Rabadão, José Saraiva da Cunha
Initial antibiotic selection was based on suspicion of causative agent and, if isolation was achieved, sensivity testing. Brucellar spondylodiscitis patients were mainly treated with a combination of doxycycline and rifampicin for 113 ± 23 days. Patients with tuberculosis vertebral infection were treated with combination therapy of isoniazid, rifampicin, pyrazinamid and ethambutol, with isoniazid and rifampicin maintenance therapy for 330 ± 186 days. S. aureus infection was treated with flucloxacillin. Half of cases of isolated strains were methicillin-resistant and in those cases a vancomycin-based regimen was used. Enterobacteriaceae infection was predominantly treated with carbapenems (63%).