Effects of Ibudilast on the Subjective, Reinforcing, and Analgesic Effects of Oxycodone in Recently Detoxified Adults with Opioid Dependence

Abstract

Ibudilast, a nonselective phosphodiesterase inhibitor, is used clinically in Asia for the treatment of asthma and poststroke dizziness. Recent preclinical studies have suggested that it also inhibits glial cell activation in rodents, and may alter opioid-mediated effects, including analgesia and withdrawal symptoms. The effects of ibudilast on the abuse potential of opioids in humans are largely unknown. The present study was designed to examine the influence of ibudilast on subjective (including drug craving), reinforcing, and analgesic effects of oxycodone in human volunteers diagnosed with opioid dependence (equivalent to moderate-severe opioid use disorder). Non-treatment-seeking opioid-dependent male volunteers (n=11) underwent an in-patient detoxification with morphine, followed by maintenance on placebo (0 mg b.i.d.) and active ibudilast (50 mg b.i.d.). Under each maintenance dose, six experimental sample and choice sessions were completed involving oral oxycodone administration (0, 15, and 30 mg/70 kg, p.o.). Subjective effects of oxycodone and drug craving were measured with visual analog scales (VAS) and a Drug Effects Questionnaire. The cold pressor test was used to produce pain, and a modified progressive-ratio choice procedure was used to measure the reinforcing effects of oxycodone. Under the active ibudilast condition compared with the placebo condition, ratings of drug liking following 15 mg of oxycodone were decreased significantly. The mean drug breakpoint value was also significantly lower in the active vs the placebo ibudilast condition under the 15 mg oxycodone condition, but not significantly lower under the 30 mg oxycodone condition. Heroin craving was significantly reduced under active ibudilast vs placebo, and similar effects were observed for tobacco and cocaine craving. Furthermore, mean subjective ratings of pain were lower in the active ibudilast condition. Our data suggest that ibudilast may be useful for treating opioid use disorders and it may enhance the analgesic effects of oxycodone.

Figure 1

Select mean subjective ratings on the visual analog scales (VAS) after the administration of 0, 15, and 30 mg/70 kg of oral oxycodone on the sample session days in the active ibudilast (closed squares) vs the placebo ibudilast (open circles) condition. *p<0.05 and **p<0.01.

Figure 2

Mean drug breakpoint values for the three available oral oxycodone doses (0, 15, and 30 mg/70 kg) during the choice sessions in the active ibudilast (closed squares) vs the placebo ibudilast (open circles) condition. *p<0.05.

Figure 3

Mean pain ratings on the ‘Painful’ and ‘Bothersome’ visual analog scales (VAS) as well as on the McGill Pain Questionnaire after administration of 0, 15, and 30 mg/70 kg oral oxycodone on the sample session days in the active ibudilast (closed squares) vs the placebo ibudilast (open circles) condition. *p<0.05.