Opioids and Neuropathic Pain

Opioids are broad spectrum analgesics that may be beneficial to alleviate the intenseperception of algesia in patients suffering with pain. They have been one of the mostcontroversial analgesics, in part because of their potential for addiction. Opioids or anycurrently available analgesic will not provide effective analgesia for every patient withchronic neuropathic pain (NP), but overall opioids are considered to be a second or thirdline class of analgesics that may provide reasonable analgesia to some patients with chronicNP. Although opioids may alleviate chronic NP, overall, NP tends to be less opioid responsivethan nociceptive pain. The mechanisms that may contribute to neuropathic pain maysimultaneously also contribute to diminishing the antinociceptive properties of opioids forneuropathic pain. Some of these mechanisms may also contribute to analgesic toleranceand/or opioid-induced hyperalgesia. Hyperalgesia consequently to nerve insult and opioidinduced analgesic tolerance, may both involve the N-methyl-D-aspartate (NMDA) receptorand share part of intracellular events producing a state of neural hyperexcitation. Conversely,opioid therapy may contribute to nociceptive processes that may be involved in neuropathicpain such as opioid-induced cholecystokinin release. Furthermore, within NP, peripheral NPappears to be the most opioid responsive, followed by spinal NP while supraspinal NP tendsto be the least responsive to opioids. Although, there is no robust evidence that any specificopioid agent is better than any other opioid at effectively treating NP, it is conceivable thatsome opioids/opioid-like analgesic agents may be particularly well suited to alleviate NP incertain patients suffering from neuropathic pain.Key words: Pain, neuropathic, opioids, oxycodone, methadone, buprenorphine,tramadol, tapentadol