Pentazocine

Pentazocine is a synthetically-prepared narcotic (opioid analgesic) drug used to treat mild to moderately severe pain. Pentazocine is sold under several brand names, such as Talwin (with naloxone) and Talacen (with acetaminophen). It should be noted that this compound may exist as one of two enantiomers, named (+)-pentazocine and (-)-pentazocine. (-)-pentazocine is a kappa-opioid receptor agonist, while (+)-pentazocine is not, and displays selectivity to the related sigma receptor.

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. It can be used as analgesics for dental extractions except in heroin addict patients.



Recreational use
In the 1980s, recreational drug users discovered that combining pentazocine with the antihistamine tripelennamine (most commonly dispensed under the brand name Pyribenzamine) 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.

Administration
Pentazocine is administered by subcutaneous, intramuscular, and intravenous injection as the lactate: The usual dose is the equivalent of pentazocine 30 to 60 mg every 3 to 4 hours; it should not be necessary to exceed 360 mg daily. It is also available in 25mg pills.

In a study published in the March 24, 2003 issue of the Proceedings of the National Academy of Sciences, a team led by McGill University researcher Jeffrey Mogil found that women with red hair require less pentazocine for pain relief than do women with other hair colours or men of any hair colour.

Legal status
Pentazocine is still classified in Schedule IV under the Controlled Substances Act in the United States, even with the addition of the naloxone. Internationally, pentazocine is a Schedule III drug under the Convention on Psychotropic Substances.