Dextromethorphan and memantine after ketamine analgesia: a randomized control trial

Area of Science:

• Neurology
• Pharmacology
• Pain Management

Background:

• Intravenous ketamine is a treatment for severe neuropathic pain.
• Prolonging pain relief with oral agents may reduce ketamine infusion frequency and hospital admissions.

Purpose of the Study:

• To assess if oral dextromethorphan or memantine can extend pain relief following intravenous ketamine.
• To evaluate the efficacy of oral N-methyl-D-aspartate receptor antagonists in managing refractory neuropathic pain.

Main Methods:

• A multicenter randomized controlled trial involving 60 patients with refractory neuropathic pain.
• Patients received dextromethorphan (90 mg/day), memantine (20 mg/day), or placebo for 12 weeks post-ketamine infusion.
• Primary endpoint was pain intensity at one month; secondary endpoints included pain, sleep, anxiety, depression, cognitive function, and quality of life up to 12 weeks.

Main Results:

• Dextromethorphan maintained ketamine pain relief at one month and reduced pain paroxysms (p=0.03).
• Pain intensity increased with memantine and placebo at one month (p=0.04).
• At three months, pain was significantly lower than baseline (p=0.001) across all groups, with no significant differences between them. Both dextromethorphan and memantine showed significant benefits in cognitive-affective domains and quality of life (p<0.05).

Conclusions:

• Oral dextromethorphan, administered after ketamine infusion, extends pain relief for one month and aids in pain coping.
• Further research with larger, pharmacogenetically stratified populations is warranted.
• Developing oral medications to prolong ketamine's antihyperalgesic effects and reduce hospital admissions is a key challenge in refractory neuropathic pain management.