Pentazocine is a synthetically-prepared prototypical mixed agonist-antagonist narcotic (opioid analgesic) drug of the benzomorphan class of opioids used to treat mild to moderately severe pain. Pentazocine is sold under several brand names, such as Fortal, Talwin NX (with naloxone), Talwin, Talwin PX (without naloxone) and Talacen (with acetaminophen). Talwin PX is the main pentazocine pharmaceutical in Canada, where laws and regulations prohibit the addition of naloxone to the formulation for non-therapeutic purposes. Related drugs include phenazocine, dezocine, and cyclazocine and several chemicals used in research on the central nervous system, and the Greek equivalent of the first letter of the name of the drug ketocyclazocine is the source of the name of the kappa opioid receptor type, as is the case with morphine and mu receptors and dynorphin and delta opioid receptors.

Development and government approval

Pentazocine was developed by the Sterling Drug Company, Sterling-Winthrop Research Institute, of Rensselaer, New York. 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. The analgesic compound was first made at Sterling in 1958. U.S. testing was conducted between 1961 - 1967. By mid 1967 Pentazocine was already being sold in Mexico, England, and Argentina, under different trade names

Adverse effects

Side effects are similar to those of morphine, but Pentazocine may be more likely to cause hallucinations and other psychotomimetic effects; cardiovascular effects make it unsuitable for use in myocardial infarction. Unlike morphine its respiratory depressant action is subject to a "ceiling" effect. 38 mg. of Pentazocine have the same pain relieving capacity as 10 mg. of morphine. It can be used as analgesics for dental extractions except in heroin addict patients.

Recreational use

In the 1970s, recreational drug users discovered that combining pentazocine with tripelennamine (a first-generation ethylenediamine antihistamine most commonly dispensed under the brand names Pelamine and Pyribenzamine and used both clinically and on the street to potentiate opioids and mitigate some of the side effects like itching, especially of codeine and morphine) produced a euphoric sensation much like that brought on by heroin. Users who were already addicted to the latter often used this combination when heroin was unavailable to them. Since tripelennamine tablets are typically blue in color, the pentazocine/tripelennamine combination acquired the slang name Ts and blues. After health-care professionals and drug-enforcement officials became aware of this scenario, the narcotic-antagonist naloxone was added to preparations containing pentazocine, and the reported incidence of its abuse has declined precipitously since. It is commonly asserted that the use of pentazocine with tripelennamine originated amongst dentists, doctors, and nurses in the Middle Western United States. A more recent development is that pentazocine is combined with methylphenidate (Ritalin) via the oral route or insufflation.