The use of the opiate antagonist, naloxone, in the treatment of intractable pain.

Thirteen adult patients with established thalamic syndrome, resistant to prior analgesic and other therapy, were treated with intravenous infusions of the opiate antagonist, naloxone. A total of twenty treatments were administered with doses of naloxone varying from 4.0-8.0 mgs. Seven patients exhibited beneficial effects with the duration of the resultant pain relief ranging from four days to two and a half years. In these patients, pain and hyperpathia were completely obtunded in six out of seven and partially in one. Side effects of therapy were minimal and of short duration being mainly confined to the cardiovascular system. During therapy all patients had continuous E.C.G. monitoring. In certain ischaemic conditions of the central nervous system, endogenous opioids possibly reduce cerebral blood flow via. inhibition of the locus coeruleus and subsequent release of noradrenaline: hence naloxone by inhibiting the opioids could increase cerebral perfusion pressure. This study has shown the benefit of treating patients with cerebral ischaemic lesions with an opioid antagonist. The rapidity of onset of pain relief in these patients would appear to indicate a mode of action by increasing cerebral perfusion.