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The clinical responses to sildenafil were evaluated and the patients were classified as good responders ( GR ) or poor responders ( PR ) when their changes in five - item version of International Index for Erectile Function questionnaire were above or below the median value .
 Chemical: sildenafil
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
 Chemical: sildenafil