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Pharmacokinetics of orally administered tramadol in domestic rabbits (Oryctolagus cuniculus)
Marcy J Souza1, Cheryl B Greenacre, Sherry K Cox
1Department of Small Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, TN 37996, USA.
Objective:
To determine the pharmacokinetics of an orally administered dose of tramadol in domestic rabbits (Oryctolagus cuniculus).
Animals:
6 healthy adult sexually intact female New Zealand White rabbits.
Procedures:
Physical examinations and plasma biochemical analyses were performed to ensure rabbits were healthy prior to the experiment. Rabbits were anesthetized with isoflurane, and IV catheters were placed in a medial saphenous or jugular vein for collection of blood samples. One blood sample was collected before treatment with tramadol. Rabbits were allowed to recover from anesthesia a minimum of 1 hour before treatment. Then, tramadol (11 mg/kg, PO) was administered once, and blood samples were collected at various time points up to 360 minutes after administration. Blood samples were analyzed with high-performance liquid chromatography to determine plasma concentrations of tramadol and its major metabolite (O-desmethyltramadol).
Results:
No adverse effects were detected after oral administration of tramadol to rabbits. Mean +/- SD half-life of tramadol after administration was 145.4 +/- 81.0 minutes; mean +/- SD maximum plasma concentration was 135.3 +/- 89.1 ng/mL.
Conclusions And Clinical Relevance:
Although the dose of tramadol required to provide analgesia in rabbits is unknown, the dose administered in the study reported here did not reach a plasma concentration of tramadol or O-desmethyltramadol that would provide sufficient analgesia in humans for clinically acceptable periods. Many factors may influence absorption of orally administered tramadol in rabbits.
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