TABLE 1

Mean (±S.E.M.) plasma levels (micrograms per milliliter) of parent drugs and their metabolites 2 h after either a single i.p. injection of heroin or morphine, or the last of 10 consecutive daily injections

Heroin
6-MAM
Morphine
M3G
M6G
Heroin (10 mg/kg) 2.2 ± 0.2 3.0 ± 0.2 2.0 ± 0.1 1.1 ± 0.1 n.d.
Repeated heroin (10 mg/kg × 10) 1.7 ± 0.2 2.7 ± 0.2 1.1 ± 0.2* 0.5 ± 0.1* 0.04 ± 0.02
Morphine (10 mg/kg) n.d. n.d. 3.0 ± 0.3 1.3 ± 0.2 n.d.
Repeated morphine (10 mg/kg × 10)
n.d.
n.d.
2.4 ± 0.2
1.2 ± 0.12
n.d.

  • n.d., not detectable.

  • ↵* P < 0.05 versus acute heroin (Tukey's test).