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Clinical data
Other namesFenazocina, Phenazocinum, DEA No. 9715
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  • (2R,6R,11R)-6,11-Dimethyl-3-(2-phenylethyl)-1,2,3,4,5,6-hexahydro-2,6-methano-3-benzazocin-8-ol
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ECHA InfoCard100.004.397 Edit this at Wikidata
Chemical and physical data
Molar mass321.464 g·mol−1
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  • C[C@H]1[C@H]2Cc3ccc(cc3[C@@]1(CCN2CCc4ccccc4)C)O
  • InChI=1S/C22H27NO/c1-16-21-14-18-8-9-19(24)15-20(18)22(16,2)11-13-23(21)12-10-17-6-4-3-5-7-17/h3-9,15-16,21,24H,10-14H2,1-2H3/t16-,21+,22+/m0/s1 ☒N
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Phenazocine (brand names Prinadol, Narphen) is an opioid analgesic drug, which is related to pentazocine and has a similar profile of effects.[2]

Effects of phenazocine include analgesia and euphoria, also may include dysphoria and hallucinations at high doses, most likely due to action at κ-opioid and σ receptors.[3] Phenazocine appears to be a much stronger analgesic with fewer side effects than pentazocine, probably due to a more favorable μ/κ binding ratio. Phenazocine is a much more potent analgesic than pentazocine and other drugs in the benzomorphan series, most probably due to the presence of an N-phenethyl substitution, which is known to boost μ-opioid activity in many classes of opioid analgesics.[4] Also, it does not cause spasm of the sphincter of Oddi, making it more suitable than morphine for the treatment of biliary or pancreatic pain.[5]

Regarding the two enantiomers of phenazocine, (R)-phenazocine[clarification needed] has twenty times the potency of morphine as an analgesic,[6] while (S)-phenazocine has about four times the potency of morphine.[7][full citation needed]


Phenazocine was invented in the 1950s.[8][9] It was one of a number of benzomorphan opioids (including pentazocine, dezocine, and cyclazocine) developed in the search for non-addictive strong analgesics.

Phenazocine was once widely used, and was mainly supplied as 5 mg tablets of the hydrobromide salt for sublingual use (Narphen, Prinadol and other names), but its use was discontinued in the United Kingdom in 2001.[10]

Phenazocine was briefly used in the United States but fell out of favor;[citation needed] it remains a Schedule II substance under the Comprehensive Drug Abuse Control & Prevention Act (Controlled Substances Act) of 1970 (CSA) but is not manufactured. The DEA ACSCN for phenazocine is 9715 and its 2013 annual manufacturing quota was 6 grams.[11]

See also[edit]

  • Tapentadol - An opioid analgesic with reduced abuse-liability


  1. ^ Anvisa (2023-03-31). "RDC Nº 784 - Listas de Substâncias Entorpecentes, Psicotrópicas, Precursoras e Outras sob Controle Especial" [Collegiate Board Resolution No. 784 - Lists of Narcotic, Psychotropic, Precursor, and Other Substances under Special Control] (in Brazilian Portuguese). Diário Oficial da União (published 2023-04-04). Archived from the original on 2023-08-03. Retrieved 2023-08-16.
  2. ^ US 2959594, "Iso-benzmorphan derivatives" 
  3. ^ Harris LS, Pierson AK (February 1964). "Some Narcotic Antagonists in the Benzomorphan Series". Journal of Pharmacology and Experimental Therapeutics. 143: 141–8. PMID 14163985.
  4. ^ Feinberg AP, Creese I, Snyder SH (November 1976). "The opiate receptor: a model explaining structure-activity relationships of opiate agonists and antagonists". Proceedings of the National Academy of Sciences USA. 73 (11): 4215–9. Bibcode:1976PNAS...73.4215F. doi:10.1073/pnas.73.11.4215. PMC 431391. PMID 186791.
  5. ^ Hopton D. (January 1971). "Double-blind clinical trial of the analgesic effects of phenazocine hydrobromide (Narphen) compared with morphine sulphate in patients with acute abdominal pain". Gut. 12 (1): 51–4. doi:10.1136/gut.12.1.51. PMC 1411461. PMID 4929685.
  6. ^ Clarke, E. G. C. (August 1959). "Identification of Phenazocine, a Potent New Analgesic". Nature. 184 (4684): 451. Bibcode:1959Natur.184..451C. doi:10.1038/184451a0. PMID 13810504. S2CID 4190489.
  7. ^ Textbook of Pharmacology - Page 117
  8. ^ Clarke EG (August 8, 1959). "Identification of Phenazocine, a Potent New Analgesic". Nature. 184 (Suppl 7): 451. Bibcode:1959Natur.184..451C. doi:10.1038/184451a0. PMID 13810504. S2CID 4190489.
  9. ^ Eckenhoff JE (May–June 1959). "Phenazocine, a new benzomorphan narcotic analgesic". Anesthesiology. 20 (3): 355–8. doi:10.1097/00000542-195905000-00016. PMID 13650222. S2CID 30670011.
  10. ^ "Monthly Release Terming and Coding Newsletter" (PDF). NHS Information Authority. February 2001. Archived from the original (PDF) on 2008-11-06. Retrieved 2008-01-11.
  11. ^ "Quotas - 2013". Diversion Control Division. Drug Enforcement Agency, U.S. Department of Justice.