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Since metformin is a substrate of both OCT3 and MATE1 , in this study we used the model of dually perfused rat placenta to investigate the role of these transporters in metformin passage across the placenta .
 Chemical: metformin; Chemical: metformin
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: metformin; Chemical: metformin