Pharmacokinetics of subcutaneously administered hydromorphone in bearded dragons (Pogona vitticeps) and red-eared slider turtles (Trachemys scripta elegans).

OBJECTIVE

To determine pharmacokinetic dosing strategy in bearded dragons (Pogona vitticeps) and red-eared sliders (Trachemys scripta elegans) based on two subcutaneously (SC) administered doses of hydromorphone (0.5 and 1.0 mg kg).

STUDY DESIGN

Randomized crossover study.

ANIMALS

Six healthy adult bearded dragons, seven healthy adult red-eared slider turtles.

METHODS

Hydromorphone (0.5 and 1.0 mg kg; 2 mg mL) was administered SC dorsolateral to the scapulae in the bearded dragons and between the head and thoracic limb of the red-eared slider turtles. Blood was collected for hydromorphone plasma concentration analysis from the ventral tail vein in bearded dragons and subcarapacial sinus in turtles before (time 0) hydromorphone administration and at 0.5, 1, 6, 12 and 24 hours.

RESULTS

The half-life of hydromorphone administered at 0.5 and 1.0 mg kg was 2.54 and 3.05 hours in bearded dragons and 2.67 and 2.01 hours in red-eared sliders, respectively. The maximum plasma concentrations for 0.5 and 1.0 mg kg were 142 and 369 ng mL in bearded dragons and 1610 and 5142 ng mL in red-eared sliders, respectively. Peak plasma concentrations were detected at 30 minutes for both species. Hydromorphone administered at both dosages provided plasma concentrations of 13-14 ng mL for at least 24 hours in bearded dragons and of 5-6 ng mL for at least 12 hours in red-eared sliders. Clinical sedation was observed for up to 1 hour posthydromorphone (1.0 mg kg) administration for five of six bearded dragons characterized by low body carriage and decreased response to stimuli. No evidence of clinical sedation was observed in red-eared sliders at either dose.

CONCLUSIONS AND CLINICAL RELEVANCE

Recommended dosing strategy for hydromorphone is 0.5 mg kg administered SC every 24 hours in bearded dragons and every 12-24 hours in red-eared sliders.