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Pentazocine
Pentazocine is a member of the benzomorphan series1 used to relieve moderate to severe pain.2 It was patented in 1960 and approved for medical use in 1964. Its pain-relieving effects have a ceiling, beyond which increasing the dose provides no additional relief. Compared with most opioids, it more frequently causes hallucinations, nightmares, and delusions. It can also cause respiratory depression1 and is habit-forming.3
Dosage & Duration
Dosage
Doses are population estimates that vary widely between individuals.
Threshold~10 mg
Light10-20 mg
Strong30-60 mg
Heavy60+ mg
Subjective Effects
Subjective Effects not written up yet
Pharmacology
Pharmacodynamics
Pentazocine acts as a κ-opioid receptor agonist and a weak μ-opioid receptor antagonist.4 Evidence suggests that its opioid antagonism involves competition at opioid receptor sites, particularly the μ receptor.5 It also acts as a sigma-1 receptor agonist. Its analgesic response has a ceiling, beyond which increasing the dose does not provide additional pain relief.
Pharmacokinetics
Pentazocine is well absorbed from the gastrointestinal tract,1 and food does not significantly change its absorption. It undergoes hepatic metabolism1 and has a reported elimination half-life of 2-3 hours. It is a substrate of P-glycoprotein, a transporter that moves drugs out of cells. Computational predictions suggest blood-brain barrier penetration, metabolism involving CYP2D6 and CYP3A4, and inhibition of CYP1A2, CYP2D6, P-glycoprotein, and renal organic cation transport; these are predicted properties rather than established experimental findings.
Metabolitesnone documented yet
Interactions
Interactions not written up yet
An unlisted combination is an unknown one, not a safe one. Check a dedicated combination chart before mixing.
Tolerance
Tolerance not written up yet
Harm Potential
Addiction & Dependence
Psychological
ModeratePentazocine is considered a habit-forming opioid depressant.
Toxicity
Pentazocine shares opioid adverse effects including drowsiness and respiratory depression; CNS depression can increase with other depressants.
Hallucinations, nightmares, delusions, and psychotomimetic effects are described as relatively frequent compared with many opioids.
At high doses, pentazocine can raise blood pressure or heart rate, and intravenous administration after myocardial infarction may add cardiac workload.
Multiple injections have caused severe injection-site necrosis and sepsis, sometimes requiring amputation; rare agranulocytosis, erythema multiforme, and toxic epidermal necrolysis are also reported.
Psychosis Risk
Pentazocine is described as fairly frequently causing hallucinations, nightmares, delusions, and psychotomimetic effects.
Seizure Risk
Pentazocine is among agents that reduce seizure threshold, but seizure frequency is not quantified.
History & Culture
Pentazocine was developed at the Sterling-Winthrop Research Institute of the Sterling Drug Company in Rensselaer, New York,7 where it was first synthesized in 1958. It was patented in 1960 and approved for medical use in 1964. It became the first mixed agonist-antagonist…
Legality
International
Pentazocine is approved and vet approved.
By Country
Illegal2
United StatesIllegalPentazocine, including its salts and any material, compound, mixture, or preparation containing any quantity unless specifically excepted or listed in another schedule, is federally controlled in Schedule IV under 21 C.F.R. § 1308.14(g)(1), effective February 9, 1979. Federal law prohibits unauthorized possession, manufacture, distribution, dispensing, import, export, and possession with intent to manufacture, distribute, or dispense; possession is permitted when the substance is obtained directly or under a valid prescription or order from a practitioner acting in professional practice, or when otherwise authorized. Pentazocine-and-naloxone tablets are currently listed as a Schedule IV human prescription drug, while the FDA lists the branded TALWIN pentazocine-lactate injection as discontinued.
CanadaIllegalPentazocine is expressly listed as a benzazocine in Schedule I, item 11(3), of the Controlled Drugs and Substances Act, S.C. 1996, c. 19, and has been subject to that classification since the Act came into force on May 14, 1997. The Schedule I classification also applies in lawful medical and licensed channels; except as authorized under the regulations, possession, import, export, possession for export, and production are prohibited, and trafficking and possession for trafficking are likewise prohibited. Unauthorized possession is punishable by up to seven years' imprisonment on indictment, with summary-conviction limits of up to $1,000 and/or six months for a first offence and up to $2,000 and/or one year for a subsequent offence. Trafficking, possession for trafficking, unauthorized import or export, possession for export, and unauthorized production are indictable offences punishable by life imprisonment.
References
Citations
Article Status
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