a mississippi senator 's personal assistant has been charged with trafficking drugs from china to use as payment for sexual favors .
police launched an investigation after seizing a package on april 9 with over a kilo of the date rape drug gbl addressed to fred pagan , office manager and personal assistant to sen. thad cochran .
pagan was paid $ 160,000 in his senate role last year , the washington post reports .
the former is punishable by five to 40 years in prison , the latter by up to 20 that