I was reading about different NMDA drugs like ketamine and dextromethadone is not an opioid drug and instead an NMDA one.
Ketamine seems to work for cluster, maybe methadone would as well?
Does anyone know if it's possible to get dextromethadone without it being part of a racemic mixture?

I know that narcotics don't work for cluster. Dextromethadone isn't a narcotic like the levomethadone is. It's an NMDA antagonist like ketamine.

alright, good to know.

Swiped from Wikipedia: Levomethadone is a full µ-opioid agonist.[citation needed] dextromethadone does not affect opioid receptor but binds to the glutamatergic NMDA (N-methyl-D-aspartate) receptor, and thus acts as a receptor antagonist against glutamate. Glutamate is the primary excitatory neurotransmitter in the CNS. NMDA receptors have a very important role in modulating long term excitation and memory formation. NMDA antagonists such as dextromethorphan (DXM), ketamine (a dissociative anaesthetic, also M.O.A+.), tiletamine (a veterinary anaesthetic) and ibogaine (from the African tree Tabernanthe iboga, also M.O.A+.) are being studied for their role in decreasing the development of tolerance to opioids and as possible for eliminating addiction/tolerance/withdrawal, possibly by disrupting memory circuitry. Acting as an NMDA antagonist may be one mechanism by which methadone decreases craving for opioids and tolerance, and has been proposed as a possible mechanism for its distinguished efficacy regarding the treatment of neuropathic pain. The dextrorotary form (d-methadone) acts as an NMDA antagonist and is devoid of opioid activity: it has been shown to produce analgesia in experimental models of chronic pain. Methadone also acted as a potent, noncompetitive α3β4 neuronal nicotinic acetylcholine receptor antagonist in rat receptors, expressed in human embryonic kidney cell li

It's listed as an open chain opioid because that's what its structure is, but doesn't have any opioid activity.

however the only non racemic mixture of methadone is for the levomethadone which is a fully binding opioid agonist, so it's not worth looking into any further.