Generic Medicine Info
Indications and Dosage
Moderate to severe pain
Adult: Initially, 50 mg 4 hourly. Dosage is individualised based on patient’s response and tolerability. Usual dosage range: 25-100 mg 3-4 hourly. Max: 600 mg daily.
Child: 6-12 years 25 mg 3-4 hourly as necessary.
Should be taken with food.
Hypersensitivity. Respiratory depression, bronchial asthma, chronic obstructive pulmonary disease, heart failure secondary to chronic lung disease, gastrointestinal obstruction, known or suspected paralytic ileus, impaired consciousness, coma, head injury or pathological brain conditions where clouding of sensorium is undesirable; raised intracranial pressure, porphyria, acute alcoholism. Concomitant use or within 14 days of discontinuing MAOI. Concurrent use with benzodiazepines.
Special Precautions
Patient with CV disease (e.g. acute MI), hypovolaemia, acute abdominal conditions, thyroid dysfunction, Addison’s disease, phaeochromocytoma, acute pancreatitis, prostatic hyperplasia, urinary stricture, toxic psychosis, delirium tremens, history of seizures disorder, history of drug abuse, sleep-related disorders. Cachectic or debilitated, and obese patient. Avoid abrupt withdrawal or dose reduction. Pregnancy and lactation.
Adverse Reactions
Significant: CNS depression, orthostatic hypotension, syncope; secondary hypogonadism, mood disorders, osteoporosis; constriction of sphincter of Oddi, raised intracranial pressure, central sleep apnoea, hypoxaemia; drug dependence, abuse and misuse; drug withdrawal syndrome, hyperalgesia.
Blood and lymphatic system disorders: Agranulocytosis, decreased WBC, eosinophilia.
Cardiac disorders: Circulatory depression, shock, palpitations, dyspnoea.
Ear and labyrinth disorders: Tinnitus.
Eye disorders: Blurred vision, miosis, diplopia, nystagmus.
Gastrointestinal disorders: Nausea, vomiting, diarrhoea, anorexia, gastrointestinal distress, xerostomia.
General disorders and administration site conditions: Malaise, weakness.
Immune system disorders: Hypersensitivity, facial oedema, Stevens-Johnson syndrome, erythema multiforme.
Injury, poisoning and procedural complications: Toxic epidermal necrolysis.
Nervous system disorders: Drowsiness, sedation, dizziness, headache, paresthesia, excitement, dysgeusia, tremor.
Psychiatric disorders: Hallucination confusion, disorientation, nightmare, euphoria.
Renal and urinary disorders: Urinary retention.
Skin and subcutaneous tissue disorders: Rash, pruritus, urticaria, dermatitis, diaphoresis.
Vascular disorders: Flushing, hypertension, hypotension, increased peripheral vascular resistance.
Potentially Fatal: Respiratory depression.
IM/IV/Parenteral/PO/SC: C
Patient Counseling Information
This medicine may cause drowsiness or dizziness, if affected, do not drive or operate machinery.
Monitoring Parameters
Monitor efficacy of pain control; blood pressure, respiratory and CNS status, bowel functions. Assess for signs and symptoms physical or psychological dependence; hypogonadism or hypoadrenalism.
Symptoms: Respiratory depression, hallucinations, seizures, hypotension, hypertension, tachycardia. In severe cases, circulatory failure, and coma. Management: Symptomatic and supportive treatment. Ensure adequate ventilation and protect the airways in consideration of gastric lavage and prevention of aspiration vomitus. Induce vomiting if patient is awake. May administer naloxone IV 0.4-2 mg, repeat every 2-3 minutes as necessary up to a total of 10 mg.
Drug Interactions
Increased CNS depressant effect with phenothiazines and TCAs. May antagonise the effect of strong opioid agonists (e.g. heroin, morphine and induce withdrawal symptoms.
Potentially Fatal: May enhance the serotonergic effect of MAOI. Increased risk of sedation, respiratory depression, coma, and death with benzodiazepines.
Food Interaction
Increased CNS depressant effect with alcohol.
Mechanism of Action: Pentazocine, an opioid benzomorphan derivative which causes analgesia, respiratory depression, and sedation similar to other opioids. It acts as an agonist at kappa opioid receptor and partial agonist action at mu opioid receptors in the CNS, causing an inhibition of ascending pain pathways which alters the perception of and response to pain.
Onset: 15-30 minutes.
Duration: ≥3 hours.
Absorption: Well absorbed from the gastrointestinal tract. Time to peak plasma concentration: 1-3 hours.
Distribution: Crosses placenta. Plasma protein binding: 60%.
Metabolism: Metabolised in the liver via oxidative and glucuronide conjugation pathways; undergoes extensive first-pass metabolism.
Excretion: Via urine (small amounts as unchanged drug). Elimination half-life: 2-5 hours.
Chemical Structure

Chemical Structure Image

Source: National Center for Biotechnology Information. PubChem Compound Summary for CID 441278, Fortral. Accessed Oct. 26, 2020.

Store below 25°C. Protect from light and moisture.
MIMS Class
Analgesics (Opioid)
ATC Classification
N02AD01 - pentazocine ; Belongs to the class of benzomorphan derivative opioids. Used to relieve pain.
Anon. Pentazocine. AHFS Clinical Drug Information [online]. Bethesda, MD. American Society of Health-System Pharmacists, Inc. Accessed 07/10/2020.

Anon. Pentazocine. Lexicomp Online. Hudson, Ohio. Wolters Kluwer Clinical Drug Information, Inc. Accessed 07/10/2020.

Buckingham R (ed). Pentazocine. Martindale: The Complete Drug Reference [online]. London. Pharmaceutical Press. Accessed 07/10/2020.

Joint Formulary Committee. Pentazocine. British National Formulary [online]. London. BMJ Group and Pharmaceutical Press. Accessed 07/10/2020.

Pentazocine Capsules BP 50 mg (Accord-UK Ltd). MHRA. Accessed 07/10/2020.

Pentazocine Tablets BP 25 mg (Accord-UK Ltd). MHRA. Accessed 07/10/2020.

Disclaimer: This information is independently developed by MIMS based on Pentazocine from various references and is provided for your reference only. Therapeutic uses, prescribing information and product availability may vary between countries. Please refer to MIMS Product Monographs for specific and locally approved prescribing information. Although great effort has been made to ensure content accuracy, MIMS shall not be held responsible or liable for any claims or damages arising from the use or misuse of the information contained herein, its contents or omissions, or otherwise. Copyright © 2024 MIMS. All rights reserved. Powered by
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