Assessment of abuse liability of Tramadol among experienced drug users: Double-blind crossover randomized controlled trial.
Level 2 - randomized trial
Individual double-blind randomized crossover trial
PubMed 28059434 · doi:10.5055/jom.2016.0361
What was done
A randomized, double-blind, complete crossover trial was conducted in 10 detoxified individuals with a history of substance abuse. Participants received three single intramuscular treatments separated by 5-day intervals: tramadol (100 mg), buprenorphine (0.6 mg), and placebo (normal saline). Subjective effects were assessed at baseline, 5, 45, and 240 minutes (120 total observations) using a modified single-dose opiate questionnaire, the Morphine Benzedrine Group (MBG) scale, the Pentobarbital Chlorpromazine Alcohol Group (PCAG) scale, and two bipolar visual analogue scales (VAS) for pleasurable effects and sedation/alertness.
What was found
Intra-group analysis showed statistically significant increases across all four subjective scales from baseline to 5, 45, and 240 minutes after both tramadol and buprenorphine; placebo scores were statistically insignificant. In inter-group comparisons, buprenorphine produced statistically higher MBG scores than tramadol at 5, 45, and 240 minutes, and significantly higher pleasurable-effect VAS scores at 45 and 240 minutes. There was no significant difference between tramadol and buprenorphine on the PCAG scale or sedation/alertness VAS. All participants liked buprenorphine most, followed by tramadol, and then placebo. Exact numerical scores, variances, and p-values were not reported in the abstract.
Why it matters
This study provides experimental human evidence that single therapeutic doses of intramuscular tramadol produce detectable abuse liability and pleasurable effects exceeding placebo in experienced substance users.
Limits
The sample size is very small (n=10), limiting statistical precision and generalizability. Findings from detoxified individuals with prior substance abuse cannot be generalized to opioid-naïve clinical populations. Only a single intramuscular dose was tested rather than typical oral therapeutic regimens, and the abstract omits quantitative point estimates and confidence intervals.