Current scientific reports on pain pharmacotherapy focus on the side effects of opioid medications related to dysregulation of the oxidative–antioxidant balance and immunomodulation. Initial observations concerned the use of opioids in the treatment of acute postoperative and cancer pain. Little is known about oxidative stress modulation in multi-modal opioid-based analgesia for chronic non-cancer pain. The aim of this study was to describe oxidative stress using plasma total antioxidant capacity (TAC) and total oxidative capacity (TOC), to assess whether these metrics are dependent on pain intensity and the scheme of analgesia. The study group consisted of patients with chronic low back pain, who were divided under the following treatments: multi-modal opioid-based therapy (n = 42), monotherapy with opioids (n = 28), and the control group (n = 11). A significantly lower TAC was observed in the study group compared to the monotherapy and control groups (220 µmol/L vs. 295 µmol/L, p = 0.02 vs. 399 µmol/L, p = 0.01). TOC was significantly lower in the polytherapy group compared to the monotherapy group (594 µmol/L vs. 723 µmol/L, p = 0.0002). A significantly lower TAC was observed in the typical analgesia scheme compared to the adjuvant analgesia model (260 µmol/L vs. 339 µmol/L, p = 0.01). The TAC in the severe pain classification was significantly lower than in the moderate group (p = 0.03). Multi-modal therapy with opioids significantly reduced oxidative activity compared to monotherapy but did not improve antioxidant capacity. Opioid-based pain therapy combined with adjuvant analgesics produced better antioxidant properties, and the antioxidant capacity was lower in severe pain scores.
Kościuczuk et al. (Thu,) studied this question.