Phenazocine Explained

Phenazocine (brand names Prinadol, Narphen) is an opioid analgesic drug, which is related to pentazocine and has a similar profile of effects.[1]

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.[2] 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.[3] 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.[4]

Regarding the two enantiomers of phenazocine, (R)-phenazocine has twenty times the potency of morphine as an analgesic,[5] while (S)-phenazocine has about four times the potency of morphine.[6]

History

Phenazocine was invented in the 1950s.[7] [8] 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.[9]

Phenazocine was briefly used in the United States but fell out of favor; 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.[10]

See also

Notes and References

  1. US . 2959594 . Iso-benzmorphan derivatives .
  2. Harris LS, Pierson AK . Some Narcotic Antagonists in the Benzomorphan Series . Journal of Pharmacology and Experimental Therapeutics . February 1964 . 141–8 . 143. 14163985.
  3. Feinberg AP, Creese I, Snyder SH . The opiate receptor: a model explaining structure-activity relationships of opiate agonists and antagonists . Proceedings of the National Academy of Sciences USA . November 1976 . 4215–9 . 73 . 11 . 186791 . 10.1073/pnas.73.11.4215 . 431391. 1976PNAS...73.4215F . free .
  4. Hopton D. . Double-blind clinical trial of the analgesic effects of phenazocine hydrobromide (Narphen) compared with morphine sulphate in patients with acute abdominal pain . Gut . January 1971 . 51–4 . 12 . 1 . 4929685 . 10.1136/gut.12.1.51 . 1411461.
  5. 10.1038/184451a0 . Identification of Phenazocine, a Potent New Analgesic . Nature . August 1959 . 184 . 4684 . 451 . Clarke . E. G. C. . 13810504 . 1959Natur.184..451C . 4190489 . free .
  6. Textbook of Pharmacology - Page 117
  7. Clarke EG . Identification of Phenazocine, a Potent New Analgesic . Nature . August 8, 1959 . 451 . 184 . Suppl 7 . 13810504 . 10.1038/184451a0. 1959Natur.184..451C . 4190489 . free .
  8. Eckenhoff JE . Phenazocine, a new benzomorphan narcotic analgesic . Anesthesiology . May–June 1959 . 355–8 . 20 . 3 . 13650222 . 10.1097/00000542-195905000-00016. 30670011 .
  9. Web site: February 2001 . Monthly Release Terming and Coding Newsletter . http://webarchive.nationalarchives.gov.uk/20081106082526/http://www.connectingforhealth.nhs.uk/systemsandservices/data/readcodes/docs/tandc0201.pdf . dead . 2008-11-06 . NHS Information Authority . 2008-01-11.
  10. Web site: Quotas - 2013 . Diversion Control Division . Drug Enforcement Agency, U.S. Department of Justice .

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