1643
After a minimum of 1 week of treatment , serum levetiracetam concentrations were measured before and 2 , 4 , and 6 hours after drug administration , and maximum and minimum serum concentrations and elimination half - life were calculated .
 Chemical: levetiracetam
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: levetiracetam