Relative abuse potential of opioid formulations in Canada: a structured field study.

Introduction: While prescription opioids can improve quality of life through pain relief they are susceptible to misuse. This field study characterizes the relative susceptibility and attractiveness of a new analgesic patch, with fentanyl embedded in a matrix material, compared to other opioid dose formulations.

Methods: Recreational opioid abusers (N = 42; 31 male, 1 female)from three Canadian sites participated in structured interviews. They were presented with nine products, some of which were hypothetical (fentanyl [F], hydromorphone [H], and oxycodone [O] in each of three formulations: matrix patch [M], reservoir-type gel patch [G], and tablet [T]). The attractiveness and tampering potential of each product was ranked using two 7-point Likert scales (Value of Product and Likelihood to Tamper), an index representing the product of the two scales, a 17-item Opiate Attractiveness Scale (OAS), relative street value, and rank order of overall desirability. Non-parametric analyses were used to compare each product to the FM.

Results: The FT, HT, and FM were highly valued and most likely to be tampered with. The products were ranked in decreasing order of desirability as follows: FT > HT > FM > FG > OT > HM > HG > OM > OG. On the OAS, FM was more attractive than all gel-patch products (p < 0.001), and OT was most attractive overall. FM was statistically similar to OT, FT, OM, and HT. Of the 42 subjects, 25 (60 percent) preferred the matrix patch to the gel patch. Of the 17 subjects who preferred the gel patch, 10 (59 percent) were from a region generally unfamiliar with that formulation.

Conclusions: Fentanyl is attractive to opioid abusers regardless of formulation. In Canada, a fentanyl matrix patch may be at higher risk for diversion, tampering, and abuse than other transdermal opioid formulations. These findings should be confirmed by epidemiological studies. Comparative risk management programs should be part of the development of any new narcotic delivery system.