Astaxanthin as a Therapeutic Candidate for Nociceptive and Inflammatory Pain: Mechanisms and Perspectives.

Recently, complementary and alternative medicine (CAM) has been actively employed for patients experiencing symptoms unresponsive to Western medical treatments like drug therapy. The natural compounds carotenoids and astaxanthin (AST) have demonstrated various beneficial biological actions for human health in several studies. Given their broad pharmacological activities and reduced toxicity, ASTs possess significant potential as resources for the development of natural analgesic drugs. Given recent studies showing that AST can modulate neuronal excitability, including nociceptive sensory transmission through voltage-gated Ca2+ channels and the n-methyl-D-aspartate (NMDA) glutamate receptor, and inhibit the cyclooxygenase-2 cascade, AST holds promise as a CAM, particularly as a therapeutic agent for nociceptive and pathological pain. Based on the in vivo research findings from our laboratory presented in this review, we have confirmed that carotenoid ASTs possess: (i) an intravenous anesthetic effect on both nociceptive and inflammatory pain comparable to existing analgesics such as ketamine; and (ii) an anti-inflammatory effect on chronic pain with an efficacy almost equivalent to that of the commonly used non-steroidal anti-inflammatory drug (NSAID) celecoxib. Therefore, these findings suggest that, as natural compounds, ASTs contribute to the relief of nociceptive and inflammatory pain, implying their potential for clinical application.