Pharmacokinetics of a single high oral dose of tramadol hydrochloride in rabbits (Oryctolagus cuniculus) is compatible with analgesic effect and innocuity
Bibliographic record
Abstract
Objective: To describe the pharmacokinetic parameters of tramadol and its main metabolites, O-desmethyltramadol (M1) and N-desmethyltramadol, and clinically detectable adverse effects after a single orally administered high dose of tramadol in rabbits (Oryctolagus cuniculus). Methods: 6 experimental and 1 control healthy intact male rabbits of commercial origin were included in February 2025. Following administration of a 30-mg/kg oral dose of tramadol, plasma concentrations of tramadol, M1, and N-desmethyltramadol were determined by UHPLC-MS at 12 predetermined time points. Pharmacokinetic parameters were calculated using commercial software. Fecal production and sedation were evaluated before and after the experiment. Results: The mean tramadol maximum plasmatic concentration was 91 ± 38 ng/mL, the average time to reach maximum plasmatic concentration was 40 minutes, the terminal half-life was 4.0 ± 2.4 hours, and the mean area under the curve from the first dose to infinity was 192 ± 45 ng/hmL. The M1 metabolite reached concentrations compatible with previously described analgesic effects in rabbits after 10 minutes and for up to 3 hours after administration in some individuals, whereas tramadol did not reach analgesic concentrations. Mild sedation was detected in 4 rabbits at the 20 minute- to 6-hour time points, and fecal production increased from 24 to 48 hours after tramadol administration. No clinically relevant adverse effects were noted. Conclusions: Administration of 30 mg/kg tramadol, PO, in rabbits results in plasma concentrations of M1 compatible with analgesia. Clinical Relevance: The short duration of action warrants further studies with long-acting formulations of tramadol.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".