Assessment of abuse liability of Tramadol among experienced drug users: Double-blind crossover randomized controlled trial

Background: Tramadol is a widely used opioid analgesic. Different preclinical, clinical, and postmarketing surveillance studies show conflicting results regarding abuse potential of this drug.Methods: A randomized double-blind complete crossover study was conducted at National Drug Dependence Treatment Centre, All India Institute of Medical Sciences, New Delhi. Total subjects were 10, comprising total 120 observations (each subject assessed at baseline, 5, 45, and 240 minutes). Subjects with history of substance abuse were included after detoxification and informed consent. Assessment was done using modified single dose opiate questionnaire, morphine benzedrine group (MBG), pentobarbital chlorpromazine alcohol group (PCAG), and two bipolar visual analogue scales (VAS) after administration of three drugs—Tramadol (100 mg), Buprenorphine (0.6 mg), and Placebo (Normal Saline) intramuscularly, at 5-day interval.Results: In intra-group analysis, there was statistically significant increase in scores of all four scales from baseline to all three time points after Tramadol and Buprenorphine administration. In inter-group analysis, statistically higher scores were seen for Buprenorphine in comparison to Tramadol at 5, 45, and 240 minutes for MBG scale; the score was significantly higher for Buprenorphine in VAS for pleasurable effect at 45 and 240 minutes, but not at baseline and 5 minutes. There was no significant difference in score at any point of time between Tramadol and Buprenorphine in PCAG scale and VAS for sedative/alertness effect. The scores were statistically insignificant in case of Placebo. All the subjects liked Buprenorphine most and then Tramadol followed by Placebo. Conclusion: Tramadol has abuse potential (even in therapeutic doses) more than Placebo but less than or comparable to Buprenorphine.