(+)-Naloxone

(+)-Naloxone (dextro-naloxone) is a drug which is the "unnatural" enantiomer of the opioid antagonist drug (−)-naloxone. Unlike "normal" naloxone, (+)-naloxone has no significant affinity for opioid receptors,[1] but instead has been discovered to act as a selective antagonist of Toll-like receptor 4. This receptor is involved in immune system responses, and activation of TLR4 induces glial activation and release of inflammatory mediators such as TNF-α and Interleukin-1.[2][3]

(+)-Naloxone
Clinical data
MedlinePlusa601092
Legal status
Legal status
  • Investigational
Identifiers
CAS Number
PubChem CID
ChemSpider
Chemical and physical data
FormulaC19H21NO4
Molar mass327.380 g·mol−1
3D model (JSmol)
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Relation of TLR4 to opioid drugs

Both "normal" and "unnatural" enantiomers of various opioid analgesic drugs including morphine, meperidine, fentanyl, methadone and buprenorphine, as well as some otherwise inactive metabolites like morphine-3-glucuronide, have been found to act as agonists of TLR4, and chronic use of these drugs consequently causes constant low-level release of TNF-α and IL-1β as well as other downstream effects. This is thought to be involved in various adverse properties of opioid analgesic drugs, such as loss of efficacy with extended use and the associated development of tolerance and dependence, as well as the development of side effects such as hyperalgesia and allodynia, which can cause long-term use of opioid analgesics to not only fail to treat neuropathic pain, but ultimately exacerbate it.[4][5]

Several opioid antagonist drugs were found to act as antagonists for TLR4, including naloxone and naltrexone. However it was found that not only the "normal" (-) enantiomers, but also the "unnatural" (+) enantiomers of these drugs acted as TLR4 antagonists (though (+)-nalmefene was inactive). Since (+)-naloxone and (+)-naltrexone lack affinity for opioid receptors, they do not block the effects of opioid analgesic drugs, and so can be used to counteract the TLR4-mediated side effects of opioid agonists without affecting analgesia,[6] though (+)-naloxone does reduce the reinforcing effects of opioid drugs.[7] (+)-Naloxone was also found to be neuroprotective,[8][9] and both (+)-naloxone and (+)-naltrexone are effective in their own right at treating symptoms of neuropathic pain in animal models.[10][11] However (+)-naloxone was also found to reduce the effects of stimulant drugs,[12][13] suggesting additional actions beyond TLR4 antagonism (possibly as a sigma receptor antagonist),[14] that might potentially result in unwanted side effects or drug interactions.

See also

References
  1. Iijima I, Minamikawa J, Jacobson AE, Brossi A, Rice KC (April 1978). "Studies in the (+)-morphinan series. 5. Synthesis and biological properties of (+)-naloxone". Journal of Medicinal Chemistry. 21 (4): 398–400. doi:10.1021/jm00202a018. PMID 206698.
  2. Wu HE, Thompson J, Sun HS, Terashvili M, Tseng LF (September 2005). "Antianalgesia: stereoselective action of dextro-morphine over levo-morphine on glia in the mouse spinal cord". The Journal of Pharmacology and Experimental Therapeutics. 314 (3): 1101–8. doi:10.1124/jpet.105.087130. PMID 15901793. S2CID 7190985.
  3. Watkins LR, Hutchinson MR, Rice KC, Maier SF (November 2009). "The "toll" of opioid-induced glial activation: improving the clinical efficacy of opioids by targeting glia". Trends in Pharmacological Sciences. 30 (11): 581–91. doi:10.1016/j.tips.2009.08.002. PMC 2783351. PMID 19762094.
  4. Hutchinson MR, Zhang Y, Shridhar M, Evans JH, Buchanan MM, Zhao TX, et al. (January 2010). "Evidence that opioids may have toll-like receptor 4 and MD-2 effects". Brain, Behavior, and Immunity. 24 (1): 83–95. doi:10.1016/j.bbi.2009.08.004. PMC 2788078. PMID 19679181.
  5. Hutchinson MR, Lewis SS, Coats BD, Rezvani N, Zhang Y, Wieseler JL, et al. (May 2010). "Possible involvement of toll-like receptor 4/myeloid differentiation factor-2 activity of opioid inactive isomers causes spinal proinflammation and related behavioral consequences". Neuroscience. 167 (3): 880–93. doi:10.1016/j.neuroscience.2010.02.011. PMC 2854318. PMID 20178837.
  6. Wu HE, Sun HS, Cheng CW, Terashvili M, Tseng LF (November 2006). "dextro-Naloxone or levo-naloxone reverses the attenuation of morphine antinociception induced by lipopolysaccharide in the mouse spinal cord via a non-opioid mechanism". The European Journal of Neuroscience. 24 (9): 2575–80. doi:10.1111/j.1460-9568.2006.05144.x. PMID 17100845.
  7. Hutchinson MR, Northcutt AL, Hiranita T, Wang X, Lewis SS, Thomas J, et al. (August 2012). "Opioid activation of toll-like receptor 4 contributes to drug reinforcement". The Journal of Neuroscience. 32 (33): 11187–200. doi:10.1523/JNEUROSCI.0684-12.2012. PMC 3454463. PMID 22895704.
  8. Liu B, Du L, Hong JS (May 2000). "Naloxone protects rat dopaminergic neurons against inflammatory damage through inhibition of microglia activation and superoxide generation". The Journal of Pharmacology and Experimental Therapeutics. 293 (2): 607–17. PMID 10773035.
  9. Liu Y, Qin L, Wilson BC, An L, Hong JS, Liu B (September 2002). "Inhibition by naloxone stereoisomers of beta-amyloid peptide (1-42)-induced superoxide production in microglia and degeneration of cortical and mesencephalic neurons". The Journal of Pharmacology and Experimental Therapeutics. 302 (3): 1212–9. doi:10.1124/jpet.102.035956. PMID 12183682. S2CID 42487051.
  10. Hutchinson MR, Zhang Y, Brown K, Coats BD, Shridhar M, Sholar PW, et al. (July 2008). "Non-stereoselective reversal of neuropathic pain by naloxone and naltrexone: involvement of toll-like receptor 4 (TLR4)". The European Journal of Neuroscience. 28 (1): 20–9. doi:10.1111/j.1460-9568.2008.06321.x. PMC 2588470. PMID 18662331.
  11. Lewis SS, Loram LC, Hutchinson MR, Li CM, Zhang Y, Maier SF, et al. (May 2012). "(+)-naloxone, an opioid-inactive toll-like receptor 4 signaling inhibitor, reverses multiple models of chronic neuropathic pain in rats". The Journal of Pain. 13 (5): 498–506. doi:10.1016/j.jpain.2012.02.005. PMC 3348259. PMID 22520687.
  12. Chatterjie N, Alexander GJ, Sechzer JA, Lieberman KW (June 1996). "Prevention of cocaine-induced hyperactivity by a naloxone isomer with no opiate antagonist activity". Neurochemical Research. 21 (6): 691–3. doi:10.1007/BF02527726. PMID 8829141. S2CID 23866510.
  13. Chatterjie N, Sechzer JA, Lieberman KW, Alexander GJ (February 1998). "Dextro-naloxone counteracts amphetamine-induced hyperactivity". Pharmacology, Biochemistry, and Behavior. 59 (2): 271–4. doi:10.1016/S0091-3057(97)00528-5. PMID 9476969. S2CID 31087300.
  14. Wu HE, Hong JS, Tseng LF (October 2007). "Stereoselective action of (+)-morphine over (-)-morphine in attenuating the (-)-morphine-produced antinociception via the naloxone-sensitive sigma receptor in the mouse". European Journal of Pharmacology. 571 (2–3): 145–51. doi:10.1016/j.ejphar.2007.06.012. PMC 2080825. PMID 17617400.
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