12861
Although much has been learned , significant gaps still exist in our understanding of the spectrum of drug metabolism and transport genes affected , gestational age - dependent changes in the activity of encoded drug metabolizing and transporting processes , and the mechanisms of pregnancy - induced alterations .
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Please list all entity words in the text that fit the category.Output format is "type1: word1; type2: word2". 
Option: Chemical 
Text: {0} 
Answer:
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