|Systematic (IUPAC) name|
|Legal status||Prohibited (S9) (AU) Class A, Withdrawn (UK) Schedule II (US)|
|Synonyms||Fenazocina, Phenazocinum, DEA No. 9715|
|Mol. mass||321.45588 g/mol|
|(what is this?)|
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.
Consequently phenazocine is some 4x the potency of morphine as an analgesic. 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.
Phenazocine was invented in the 1950s. 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.
Phenazocine was briefly used in the United States but fell out of favour for the above-mentioned reasons;[which?] it remains a Schedule II substance under the Comprehensive Drug Abuse Control & Prevention Act (aka Controlled Substances Act) of 1970 (CSA) but is not manufactured; other Schedule II narcotics not in use in the United States include bezitramide and metopon. The DEA ACSCN for phenazocine is 9715 and its 2013 annual manufacturing quota was 6 grammes 
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