the relative permeability coefficients of three phenylpiperidine analogues , meperidine , fentanyl , and sufentanil , all measured on a single piece of skin , were 3.7 x 10 ( -3 ) , 5.6 x 10 ( -3 ) , and 1.2 x 10 ( -2 ) cm/hr , respectively .
C0015846
fentanyl
C0143993
sufentanil