Nalbuphine is a mixed opioid agonist-antagonist that acts primarily as a κ-opioid receptor agonist and μ-opioid receptor antagonist, providing pain relief and potential reduction in cluster headache severity. Its unique pharmacodynamic profile allows for analgesic effects with potentially lower risk of respiratory depression and addiction compared to pure μ-opioid agonists, making it a possible alternative treatment for acute cluster headache management.