Low-dose intrathecal naloxone to enhance intrathecal morphine analgesia: a case report.

Ultra low doses of opioid antagonists such as naloxone block excitatory opioid receptor pathways may paradoxically enhance morphine analgesia. This case study reports safety and efficacy of ultra low-dose intrathecal (IT) naloxone added to IT morphine for the treatment of severe refractory chronic low back pain. A 56-year-old man with a history of severe chronic low back pain (post-laminectomy syndrome) was evaluated. Extensive multidisciplinary therapies had all failed. Initial treatment at our clinic was a lumbar IT trial of morphine (unsuccessful) up to 50 mg/day. We administered an IT bolus of morphine 2 mg combined with IT naloxone of 20 ng with the patient's consent and approval. The onset of pain relief was within 20 minutes and peaked at 1 hour with a 50 percent reduction in VAS pain score. There were no signs of adverse drug toxicity or hemodynamic compromise. An IT infusion of daily morphine 5 mg and naloxone 50 ng was started. Throughout the 3-year follow-up period, the patient maintained pain reduction of 60 to 80 percent, with a return to daily activities and no further hospitalizations.