1192
METHODS : We performed a systematic , retrospective study comparing active or former intravenous drug users receiving methadone and those not receiving methadone among all patients hospitalized over a 5 - year period in a tertiary care hospital .
 Chemical: methadone; Chemical: methadone
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: methadone; Chemical: methadone