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Updated 2 Feb 2023 | Opioid analgesics


Tablets containing 25mg pentazocine hydrochloride
Capsules containing 50mg pentazocine hydrochloride

Drugs List

  • pentazocine 25mg tablets
  • pentazocine 50mg capsules
  • Therapeutic Indications


    For the relief of moderate to severe pain.


    Not all available brands are licensed for all age groups.


    The usual initial dosage is 50mg every 3 to 4 hours preferably after food. The usual dosage range is 25-100mg every 3 to 4 hours.

    The maximum daily dosage is 600mg.


    See Adult Dose

    Where there is evidence of hepatic and or renal impairment the dosage should be reduced as appropriate.


    Only the tablet formulation (25mg) is recommended and licensed for children under 12 years of age

    The usual dosage is 25mg every 3 to 4 hours as required.

    Pentazocine is not recommended for children under 6 years of age.

    Patients with Renal Impairment

    Use with caution and at reduced dose in patients with renal impairment as both pentazocine and its metabolites are cleared renally to some extent. Side effects may be accentuated.

    Patients with Hepatic Impairment

    Use with caution and at reduced dose in patients with hepatic impairment as pentazocine is extensively metabolised by the liver. Side effects may be accentuated. Opiate analgesics may precipitate coma in hepatic impairment.


    For oral administration

    Pentazocine should be administered with or after food.


    Raised intracranial pressure
    Head trauma
    Brain disorder - where clouding of the sensorium is undesirable
    Acute alcohol intoxication


    Respiratory depression
    Acute asthma
    Cardiac failure secondary to chronic lung disease

    Children under 6 years of age

    Within 2 weeks of discontinuing MAOIs

    Precautions and Warnings

    Opioid dependence or patients taking other opiates. Pentazocine has both agonist and antagonist properties and as such may precipitate withdrawal reactions or pain in patients taking other opioids.

    Renal impairment
    Hepatic impairment

    Pregnancy (see Pregnancy)
    Breastfeeding (see Lactation)

    Elderly - reduce dose
    Children under 12 years - only the 25mg tablets are licensed for this age group

    Recent myocardial infarction - pentazocine may increase heart rate and blood pressure
    Cardiac arrhythmias

    Phaeochromocytoma - pentazocine may increase heart rate and blood pressure
    Adrenocortical insufficiency



    Inflammatory bowel disorders
    Obstructive bowel disorders

    Prostate disorders - Prostatic hypertrophy

    Patients should be advised to avoid alcohol during treatment with pentazocine

    Patients should be advised that their ability to drive and operate machinery may be compromised during treatment

    Some formulations contain lactose, caution in galactosaemia, glucose-galactose malabsorption syndrome and lactose intolerance.

    Use in Porphyria

    Contraindicated in porphyria

    Pregnancy and Lactation


    Use with caution in pregnancy. There is no epidemiological evidence for the safety of pentazocine in human pregnancy, but it has been widely used for many years without apparent ill consequences.

    Pentazocine crosses the placenta and into the foetal circulation. Opioid effects including central depression and abstinence syndrome may be seen in the foetus and newborn. It does not appear to have significant adverse effects on uterine function at parturition.

    Animal studies showed harmful effects in foetal rodents but only at doses which also produced maternal toxicity.

    The use of all medication in pregnancy should be avoided whenever possible; particularly in the first trimester. Non-drug treatments should also be considered. When essential, a medication with the best safety record over time should be chosen, employing the lowest effective dose for the shortest possible time. Polypharmacy should be avoided. Teratogens taken in the pre-embryonic period, often quoted as lasting until 14-17 days post-conception, are believed to have an all-or-nothing effect. Where drugs have a short half-life, and when the date of conception is certain, this may allow women to be reassured where drug exposure has occurred within this time frame. Further advice may be available from the UK National Teratology Information Service (NTIS) and through ToxBase, available via password on the internet ( ) or if this is unavailable at the backup site ( ).


    Use with caution in lactation.

    Pentazocine is excreted in small amounts in breast milk so it is recommended that infants of nursing mothers receiving high doses of pentazocine be appropriately monitored.

    Neonates, infants born prematurely, those with low birth weight, those with an unstable gastrointestinal function or who have serious illnesses may require special consideration. For any infant, if a drug is prescribed to the nursing mother, it should be at the lowest practical dose and for the shortest time. When drug administration is unavoidable and breastfeeding is to continue, minimisation of exposure of the infant to the drug may sometimes be achieved by timing the maternal doses to just after a feeding episode. Infants exposed to drugs via breast milk should be monitored for unusual signs or symptoms. Interactions between the drug received by the infant from the mother's milk and medication prescribed for the infant should also be considered, for example, when the drug given to the infant may prevent metabolism of the drug received via breast milk.
    Specialist advice is available from the UK Drugs in Lactation Advisory Service at

    Effects on Ability to Drive and Operate Machinery

    This class of medicine is in the list of drugs included in regulations under 5a of the Road Traffic Act 1988 (England and Wales). When prescribing this medicine: Advise patient the medicine can affect cognitive function and is likely to affect ability to drive. Advise patient not to drive until they know how the medicine affects them.


    Patients should be advised to avoid alcohol during treatment with pentazocine

    Patients should be advised that their ability to drive and operate machinery may be compromised during treatment

    Side Effects

    Visual disturbances
    Dry mouth
    Respiratory depression
    Mood changes
    Biliary spasm
    Urinary retention
    Hypertension (transient)
    Altered uterine contractions
    Allergic reaction
    Toxic epidermal necrolysis
    Circulatory depression
    Raised intracranial pressure
    Reduced libido
    Facial oedema
    Blood disorders
    Abdominal pain
    Ureteric spasm


    It is strongly recommended that the UK National Poisons Information Service be consulted on cases of suspected or actual overdose where there is doubt over the degree of risk or about appropriate management.

    The following number will direct the caller to the relevant local centre (0844) 892 0111

    Information may be obtained if you have access to ToxBase the primary clinical toxicology database of the National Poisons Information Service. This is available via password on the internet ( ) or if this is unavailable at the backup site ( ).

    Shelf Life and Storage

    Store below 25 degrees C
    Protect from light
    Store in a dry place

    Reference Sources

    British National Formulary, 62nd Edition (2011) Pharmaceutical Press, London.

    BNF for Children (2011-2012) Pharmaceutical Press, London.

    Drugs During Pregnancy and Lactation: Treatment Options and Risk Assessment, 2nd edition (2007) ed. Schaefer, C., Peters, P. and Miller, R. Elsevier, London.

    Drugs in Pregnancy and Lactation: A Reference Guide to Fetal and Neonatal Risk, 9th edition (2011) ed. Briggs, G., Freeman, R. and Yaffe, S. Lippincott Williams & Wilkins, Philadelphia.

    Martindale: The Complete Drug Reference, 37th edition (2011) ed. Sweetman, S. Pharmaceutical Press, London.

    Summary of Product Characteristics: Pentazocine 25mg Tablets, Actavis. Revised July 2011

    Summary of Product Characteristics: Pentazocine 50mg Capsules, Actavis. Revised July 2011

    US National Library of Medicine. Toxicology Data Network. Drugs and Lactation Database (LactMed).
    Available at:
    Pentazocine Last revised: January 4, 2011
    Last accessed: February 1, 2012 Government departments. Department for Transport. Publications. Drug driving and medicine: advice for healthcare professionals. Drug driving: Guidance for healthcare professionals on drug driving. Available at: Last accessed: 6 January 2015 New drug driving offence implications for medicines packaging. Medicines Regulatory News. 10 December 2013. Available at: Last accessed: 6 January 2015

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