Methadone

Methadone is a unique opioid agonist. While it possesses the full opioid agonist properties of morphine is similar in potency, it also has an affinity for N-methyl-D-aspartate (NMDA) receptors, meaning that it may have some potential to prevent central sensation or “wind-up” in a fashion similar to ketamine. Vomiting upon intramuscular injection is less common and not expected at clinically relevant doses. Sedative properties of methadone tend to be less when compared to morphine used at an equivalent dose rate.