Opioid Therapy and Implications for Oxidative Balance: A Clinical Study of Total Oxidative Capacity (TOC) and Total Antioxidative Capacity (TAC).

BACKGROUND: Opioids are used in pharmacotherapy for chronic pain. The phenomenon of their influence on the oxidative-antioxidant balance is poorly understood. Additionally, little is known about the oxidative status in patients receiving chronic opioid noncancer pain therapy.

METHODS: The primary goal was to explore oxidative status using the total oxidative capacity (TOC) and total antioxidative capacity (TAC) in patients with chronic lower back pain (LBP) treated with opioids. The secondary task was to present the risk factors connected with the duration of therapy or anthropometric parameters. Plasma TOC and TAC were analyzed in the study group (n = 28), i.e., patients with chronic LBP treated with opioids, and in the control group (n = 11), i.e., healthy volunteers.

RESULTS: The TAC was significantly lower in the study group compared to the control group ( p < 0.05), while the TOC did not differ significantly. A statistically lower TOC for buprenorphine compared to oxycodone ( p = 0.019) and tramadol ( p = 0.036) was observed. The TOC did not differ between tramadol and oxycodone. The highest TAC was described for oxycodone, while the TAC for buprenorphine and tramadol was significantly lower in comparison with oxycodone ( p = 0.007 and p = 0.016). The TOC/TAC ratio was higher in patients with nicotinism in both groups.

CONCLUSIONS: Patients receiving chronic opioid therapy presented a lower antioxidative capacity. There were differences in opioid-induced oxidative imbalance, which is very important clinically. Nicotinism increases the oxidative-antioxidative imbalance. The least oxidative capacity was associated with buprenorphine, while oxycodone showed the greatest antioxidant activity. The most favorable TOC/TAC ratio was observed for buprenorphine. It is suggested that buprenorphine or oxycodone has the best profile, and there is no correlation with the duration of opioid therapy or the opioid dose. However, all opioid substances can potentially enhance the oxidative-antioxidative status.