1953
All participants received 1 . 0 mg or 2 . 0 mg trihexyphenidyl or placebo administered in counterbalanced sequences over a period of three consecutive weeks .
 Chemical: trihexyphenidyl
Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Disease, Chemical 
Text: {0} 
Answer:
 Chemical: trihexyphenidyl