Fig. 1.

Mice (N=5–9/dose) were injected with hydromorphone (0.2–1.25 mg/kg s.c.) and tested for antinociception (tail flick) at various time points (15–240 min). Each time action profile was determined once except for the 0.3125mg/kg dose which was determined twice and the combined data (mean + S.E.M.) are presented. Hydromorphone’s time of peak analgesic effect was estimated as 45 min.