Respiratory depression is a common side effect, but is subject to a ceiling effect, such that at a certain dose the degree of respiratory depression will no longer increase with dose increases. Likewise rarely it has been associated with agranulocytosis, erythema multiforme and toxic epidermal necrolysis. Tissue damage at injection sites
Severe injection site necrosis and sepsis has occurred (sometimes requiring amputation of limb) with multiple injection of pentazocine lactate. In addition, animal studies have demonstrated that Pentazocine is tolerated less well subcutaneously than intramuscularly. History
Pentazocine was developed by the Sterling Drug Company, Sterling-Winthrop Research Institute, of Rensselaer, New York. The analgesic compound was first made at Sterling in 1958. U.S. testing was conducted between 1961 and 1967.It was approved by the Food and Drug Administration in June 1967 after being favorably reviewed following testing on 12,000 patients in the United States. By mid 1967 Pentazocine was already being sold in Mexico, England, and Argentina, under different trade names. Society and culture
Legal status
Pentazocine was originally unclassified under the Controlled Substances Act. A petition was filed with the Drug Enforcement Administration on October 1, 1971, to shift it to Schedule III. The petition was filed by Joseph L. Fink III, a pharmacist and law student at Georgetown University Law Center as part of the course Lawyering in the Public Interest. That petition was accepted for review on November 10, 1971. D.E.A. published a Final Rule transferring it to schedule IV on January 10, 1979, with an effective date of February 9, 1979.
This is understood to be the first instance of a successful petition to reclassify a substance under the relatively recently enacted Controlled Substances Act. Pentazocine is still classified in Schedule IV under the Controlled Substances Act in the United States, even with the addition of Naloxone. Some states classify it in Schedule II, such as Illinois and South Carolina (injectable form only), or Schedule III such as Kentucky.) Internationally, pentazocine is a Schedule III drug under the Convention on Psychotropic Substances. Pentazocine has a DEA ACSCN of 9720; being a Schedule IV substance, the DEA does not assign an annual manufacturing quota for pentazocine for the United States. Brand names
Pentazocine is sold under several brand names, such as Fortral, Sosegon, Talwin NX (with naloxone), Talwin, Talwin PX, Fortwin and Talacen (with paracetamol (acetaminophen)). See also
Cyclazocine (hallucinogenic)
Volazocine

References
External links
Eurekalert report on PNAS article