2724
Following a 3 - week observation period , volunteers were treated with zidovudine 600 mg / day for 18 weeks , 900 mg / day for 9 weeks and 1200 mg / day for 9 weeks , followed by a washout period of 6 weeks after which they were re - started on 1200 mg / day or the highest tolerated dose at 8 - hourly intervals .
 Chemical: zidovudine
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: zidovudine