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The subjects were randomly allocated to receive 0 . 5 microg / kg / min GTN or placebo over 20 min on two headache - free days .
 Chemical: GTN; Disease: headache
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: GTN; Disease: headache