Table 1.

Permeability [cm/s] across the cells at 120 min for opioids tested individually or in mixtures.

	Permeability (cm/s)*10-5
Single doses
Morphine	0.36 ± 0.16
Heroin	0.21 ± 0.10
Fentanyl	1.76 ± 0.48
Methadone	0.58 ± 0.22
Oxycodone	2.46 ± 0.031
Naloxone	2.09 ± 0.50
Mixed doses
Heroin + fentanyl	H: 0.066* ± 0.066; F: 1.76 ± 0.48
Heroin + methadone	H: 0.23 ± 0.14; M: 0.59 ± 0.20
Morphine + naloxone	M: 0.32 ± 0.19; N: 1.93 ± 0.57

Note: Permeability was significantly decreased (P < 0.05) for heroin when administered together with fentanyl as indicated by ‘*’.