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Since ethambutol is actively excreted via the renal system, compromise of renal function such as due to renal tuberculosis may lead to serum concentration elevations of ethambutol sufficient to produce optic neuropathy.
 ( adverse event: lead ,  serum concentration elevations of ethambutol sufficient to produce optic neuropathy: Effect, ethambutol: Treatment, ethambutol: Treatment.Drug) 
Locate the role in the text that participated in the event based on the event type and return it in the event list. 
 Option: Event type: adverse event,potential therapeutic event, Arguments type: Treatment.Disorder,Treatment.Time_elapsed,Treatment.Dosage,Subject.Race,Treatment.Drug,Treatment.Route,Subject.Disorder,Treatment.Freq,Treatment,Effect,Subject.Population,Treatment.Duration,Combination.Drug,Subject,Subject.Age,Subject.Gender. 
Text: {0} 
Answer:
 ( adverse event: lead ,  serum concentration elevations of ethambutol sufficient to produce optic neuropathy: Effect, ethambutol: Treatment, ethambutol: Treatment.Drug) 