18513
Participants were selected out of a group of volunteers , based on their performance on a memory screening and they were orally treated with vardenafil ( 10 - 20 mg or placebo ) .
 Chemical: vardenafil
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: vardenafil