ArticleIndian journal of psychiatry2026
Urine tapentadol quantification in people injecting supratherapeutic doses: Clinical utility and liquid chromatography-tandem mass spectrometry method validation.
Article in Indian journal of psychiatry, 2026. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Not yet cited in PubMed.
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Abstract
Background: Tapentadol, a dual-action opioid, is increasingly misused in India by intravenous injection of crushed tablets. Objective urine testing is scarce, and pharmacokinetic data for injected supratherapeutic use are limited. Aim: To validate a practical liquid chromatography-tandem mass spectrometry (LC-MS/MS) urine assay, estimate optimal detection time-points in clinical settings, and define concentration cut-offs at those time-points. Methods: We interviewed people with injecting Tapentadol use for last-use details (time since use, dose). Multiple urine specimens were collected (May 2023-Feb 2024). LC-MS/MS quantification was validated using UNODC guidelines. Optimal thresholds and maximal accuracy were estimated at prespecified clinically relevant time-points (24, 72, 120, and 168 hours). Results: We analyzed 778 samples from 342 male patients; median age 24 years (IQR 22-26). Median daily Tapentadol dose 1,000 mg (IQR 500-1500); median injection frequency 10/day (IQR 8-15); median last-use-dose 300 mg (IQR 200-500). Urine concentrations declined exponentially over time. Analytical performance: linearity r² > 0.998 (50-1000 ng/mL), negligible carryover, matrix effect ≤10%, and limit of quantification 1 ng/mL. Accuracy was highest at 72 hours with an optimal concentration cut point of 205 ng/mL (sensitivity 1.00, specificity 0.98, and accuracy 0.99). Conclusion: We report a feasible, validated LC-MS/MS urine assay for Tapentadol with good performance at clinically relevant time-points, best performance being at 72 hours after last use. Tapentadol concentration decreased exponentially over time (first-order elimination kinetics), but remained detectable beyond 48 hours, possibly due to saturation kinetics with supratherapeutic-dose IV use or the impact of excipients. These concentration thresholds can support objective monitoring of abstinence/relapse in clinical care.
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