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Male volunteers ( n=12) participated in a randomised, two-period, crossover trial evaluating the effect of multiple doses of 600 mg rifampicin once daily for 7 days on repaglinide metabolism.
 ( adverse event: on ,  Male volunteers ( n=12): Subject, Male: Subject.Gender, n=12: Subject.Population, repaglinide metabolism: Effect, multiple doses of 600 mg rifampicin once daily for 7 days: Treatment, multiple doses of 600 mg: Treatment.Dosage, rifampicin: Treatment.Drug, once daily: Treatment.Freq, 7 days: Treatment.Duration) 
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: on ,  Male volunteers ( n=12): Subject, Male: Subject.Gender, n=12: Subject.Population, repaglinide metabolism: Effect, multiple doses of 600 mg rifampicin once daily for 7 days: Treatment, multiple doses of 600 mg: Treatment.Dosage, rifampicin: Treatment.Drug, once daily: Treatment.Freq, 7 days: Treatment.Duration) 