Methadone and Ketamine for Neuropathic Pain Treatment

Management of Neuropathic Chronic Pain With Methadone Combined With Ketamine: Randomized, Double Blind, Active-controlled Clinical Trial

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.

The solution of methadone was prepared by mixing 10 ml of methadone (10 mg/ml) and 90 ml of saline 0.9% (Baxter, São Paulo, Brazil)

The solution of ketamine was prepared by mixing 20 ml of S(+)-ketamine hydrochloride (50 mg/ml, Cristália®, São Paulo, Brazil) and 80 ml of saline 0.9% (Baxter, São Paulo, Brazil), obtaining a concentration of 10 mg/ml of ketamine.

the solution of methadone, ketamine was prepared by mixing 10 ml of methadone hydrochloride (10 mg/ml, Cristália®, São Paulo, Brazil), 20 ml of S(+)-ketamine hydrochloride (50 mg/ml, Cristália®, São Paulo, Brazil) and 70 ml of saline 0.9% (Baxter, São Paulo, Brazil), obtaining a concentration of 1 mg/ml of methadone and 10 mg/ml of ketamine.

The secondary outcomes were the presence of burning and/or shooting pain, allodynia and 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