1441
Results from clinical studies suggest that pregnancy alters hepatic drug metabolism in a cytochrome P450 ( P450 ) isoform - specific manner , and rising concentrations of female hormones are potentially responsible for the changes .
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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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