Methadone and ketamine are effective for neuropathic pain management. However, the benefits of the association of both drugs are uncertain. Here, the investigators conducted a randomized, double-blind, in parallel, active controlled clinical trial to test the hypothesis that methadone combined ketamine (methadone/ketamine) is more effective than methadone or ketamine alone in reducing neuropathic pain.

Either oral methadone or ketamine have been used in neuropathic pain management, however, the benefits of the association of both drugs are uncertain. Here, we conducted a randomized, double-blind, in parallel, active controlled clinical trial to test the hypothesis that methadone combined ketamine (methadone/ketamine) is more effective than methadone or ketamine alone in reducing neuropathic pain.

Methods: Fourthly two patients with neuropathic pain refractory to conventional therapy were randomly assigned to receive during three months oral methadone (n= 13), ketamine (n=13) or methadone combined with ketamine (n=13). The primary outcome was pain score on visual analogical scale (VAS) assessed on baseline, 8, 15, 30, 60 and 90 days throughout the treatment, and the secondary outcomes were symptoms of neuropathic pain such as allodynia, burning or shooting pain as well the side effects.

Inclusion Criteria:

• patients complaining of pain for more than 6 months with neuropathic pain poorly responsive to drugs used to treat neuropathic pain (i.e. opioid, non-opioid, anticonvulsants, antidepressants), who were 22 to 77 years old

Exclusion Criteria:

• patients with a history of severe psychiatric disorder,
• misuse of illegal drugs or
• hepatic disease