30498
In the present study , we investigate the influence of glycerol and urea on the permeability of a model drug ( metronidazole , Mz ) across excised pig skin membranes at different hydrating conditions .
 glycerol, urea, metronidazole
Please list all entity words in the text that fit the category. Output format is "word1, word2". 
Option: Chemical 
Text: {0} 
Answer:
 glycerol, urea, metronidazole