Table 1.

Fold stimulation of basal P-gp-ATPase activity by a series of morphine and meperi-dine analogs.

Compound	n	Fold stimulation
Morphine analogs
Non-treated (control)	4	1.00 ± 0.04
Morphinea	4	1.54 ± 0.08b
N-Benzylcodeinec	4	1.01 ± 0.14
6-Desoxymorphined	4	1.01 ± 0.11
Oxymorphonee	4	1.12 ± 0.12
Thevinonef	4	1.28 ± 0.05b
Methyl thevinolf	4	1.28 ± 0.04b
Etorphine-3-methyl etherf	4	1.29 ± 0.10
6-Desoxycodeined	4	1.31 ± 0.15
Etorphinef	4	1.34 ± 0.08b
Codeinea	4	1.36 ± 0.07b
Naloxonea	4	1.25 ± 0.11
Naltrexonea	4	1.13 ± 0.05
Meperidine analogsg
Non-treated (control)	4	1.00 ± 0.03
Meperidine	3	1.51 ± 0.29
N-Phenylbutyl normeperidine	3	1.10 ± 0.23
N-Propyl normeperidine	3	1.81 ± 0.23b
N-2-Methylpropyl normeperidine	3	1.88 ± 0.22b
N-Methylallyl normeperidine	3	2.00 ± 0.41b
N-Butyl normeperidine	3	2.06 ± 0.19b
N-Phenylpropyl normeperidine	3	2.38 ± 0.12b
N-Crotyl normeperidine	3	2.80 ± 0.13b
N-Benzyl normeperidine	3	2.94 ± 0.07b
N-Allyl normeperidine	3	2.95 ± 0.29b
N-Phenylethyl normeperidine	3	3.66 ± 0.15b

Results are represented as mean ± S.E.M. The positive controls, verapamil and methadone stimulated the P-gp basal activity by 5.41 ± 1.52 and 2.45 ± 0.27-folds (Hassan et al., 2009), respectively.

^aIndicates compounds purchased or supplied as gifts from Mallinckrodt, Inc. (St. Louis, MO).

^bIndicates significant differences (p < 0.05) from corresponding control as determined by Student’s t-test.

^cIndicates a compound synthesized according to Koczka and Bernath (1958).

^dIndicates compounds synthesized according to Rapoport and Bonner (1951).

^eIndicates a compound synthesized according to Iijima et al. (1978).

^fIndicates compounds synthesized according to Bentley et al. (1967).

^gMeperidine analogs data were previously reported as change in luminescence (Mercer et al., 2007) and represented in the table for comparison with the morphine analogs.