Pentazocine; Uses, Dosage, Side Effects, Interactions

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Pentazocine Hydrochloride is the hydrochloride salt form of pentazocine, a benzomorphan narcotic agonist-antagonist. Pentazocine hydrochloride binds to and activates kappa- and sigma-opioid receptors, resulting in sedation and analgesia. In addition, this agent antagonizes the mu-receptor. Pentazocine hydrochloride partially reverses opiate-induced cardiovascular, respiratory, and behavioral depression.

Pentazocine is a synthetic opioid with both agonist and antagonist activity against opiate receptors which is used in oral and parenteral forms as an analgesic for moderate-to-severe pain. Pentazocine has not been linked to serum enzyme elevations during therapy or to clinically apparent liver injury.

Mechanism of Action of Pentazocine

The preponderance of evidence suggests that pentazocine antagonizes the opioid effects by competing for the same receptor sites, especially the opioid mu receptor.

Pentazocine is a potent analgesic which when administered orally in a 50 mg dose appears equivalent in analgesic effect to 60 mg (1 grain) of codeine. The onset of significant analgesia usually occurs between 15 and 30 minutes after oral administration, and the duration of action is usually three hours or longer. Onset and duration of action and the degree of pain relief are related both to dose and the severity of pretreatment pain. Pentazocine weakly antagonizes the analgesic effects of morphine and meperidine; in addition, it produces an incomplete reversal of cardiovascular, respiratory, and behavioral depression induced by morphine and meperidine. Pentazocine has about 1/50 the antagonistic activity of nalorphine. It also has sedative activity.

Indications of Pentazocine

Contra-Indications of Pentazocine

  • Systemic mastocytosis
  • Brain tumor
  • Untreated decreased level of thyroid hormones
  • Addison’s disease
  • Extreme loss of body water
  • Psychosis caused by Sudden Alcohol Withdrawal
  • Psychosis caused by a poisonous agent
  • Mood changes
  • Having thoughts of suicide
  • Addiction to a drug
  • Alcohol intoxication
  • Drug abuse
  • Slow heartbeat
  • Abnormal heart rhythm
  • Abnormally low blood pressure
  • Emphysema
  • Decreased lung function
  • Stomach or Intestinal Tract Operation
  • Ulcerated Colon
  • Inflammatory bowel disease
  • Constipation
  • Liver problems
  • Disease of the Gallbladder
  • Spasm of a bile duct tract
  • Kidney disease with a reduction in kidney function
  • Narrowing of the Tube that Empties Urine From the Bladder
  • Enlarged Prostate
  • Coma
  • Seizures
  • Shock
  • Can not empty bladder
  • Weakened Patient
  • High pressure within the skull
  • Intense Abdominal Pain
  • Morbid Obesity
  • Asthma That Is Getting Worse
  • Allergies to Pentazocine

Dosage of Pentazocine

Strengths: 30 mg/mL


  • Initial dose: 30 mg IM/IV/subcutaneously; may repeat dose every 3 to 4 hours
  • Maximum single doses: 30 mg (IV); 60 mg (IM or subcutaneously)
  • Maximum daily dose: 360 mg


  • Initial dose: 30 mg IM/IV/subcutaneously; may repeat dose every 3 to 4 hours
  • Maximum single doses: 30 mg (IV); 60 mg (IM or subcutaneously)
  • Maximum daily dose: 360 mg

Labor Pain

  • Initial dose: 30 mg IM or 20 mg IV
  • Two or three additional 20 mg IV doses may be given at 2 to 3-hour intervals as needed when contractions become regular

Pediatric Dose for Anesthesia

  • Initial dose: 0.5 mg/kg IM once

Pediatric Dose for Pain

  • Age: 16 years or older
  • Initial dose: 30 mg IM/IV/subcutaneously; may repeat dose every 3 to 4 hours
  • Maximum single doses: 30 mg (IV); 60 mg (IM or subcutaneously)
  • Maximum daily dose: 360 mg

Side Effects of Pentazocine

More Common

  • False or unusual sense of well-being
  • nausea
  • vomiting


  • Blistering, crusting, irritation, itching, or reddening of the skin
  • blue-green to black skin discoloration
  • bluish lips or skin
  • blurred vision
  • burning, crawling, itching, numbness, prickling, “pins and needles”, or tingling feelings
  • cold, clammy skin
  • confusion
  • cough
  • cracked, dry, or scaly skin
  • the decrease in the frequency of urination
  • the decrease in urine volume
  • depression
  • difficult or troubled breathing
  • difficulty in passing urine (dribbling)
  • dizziness
  • fainting
  • fast or slow heartbeat
  • fast, weak pulse
  • flushed skin
  • hardening or thickening of the skin
  • headache
  • increased sweating
  • irregular, fast, slow, or shallow breathing
  • lightheadedness
  • nervousness
  • pain, redness, or sloughing of the skin at the injection site


  • Change in taste
  • confusion about identity, place, and time
  • constricted, pinpoint, or small pupils (black part of the eye)
  • double vision
  • seeing double seeing, hearing, or feeling things that are not there
  • stomach cramps
  • trouble sleeping
  • uncontrolled eye movements

Drug Interactions of Pentazocine

Pentazocine may interact with following drugs, supplements & may change the efficacy of drugs

  • alcohol
  • anesthetics
  • antihistamines (e.g., cetirizine, dimenhydrinate, diphenhydramine, hydroxyzine)
  • antipsychotic medications (e.g., olanzapine, quetiapine, risperidone)
  • baclofen
  • barbiturates (e.g., phenobarbital, secobarbital)
  • benzodiazepines (e.g., alprazolam, diazepam, lorazepam)
  • benztropine
  • brimonidine
  • bupropion
  • cyclobenzaprine
  • dantrolene
  • desmopressin
  • dextroamphetamine
  • diamorphine
  • diphenoxylate
  • flavoxate
  • gabapentin
  • guanfacine
  • ipratropium
  • methadone
  • methocarbamol
  • mirtazapine
  • monoamine oxidase inhibitors (e.g, tranylcypromine, phenelzine, moclobemide) taken within the past 14 days
  • octreotide
  • orphenadrine
  • other narcotic analgesics (e.g., codeine, morphine)
  • oxybutynin
  • phenothiazines (e.g., perphenazine, thioridazine)
  • pregabalin
  • sedatives and tranquilizers
  • seizure medications (e.g., carbamazepine, lamotrigine, phenytoin, primidone)
  • selective serotonin reuptake inhibitors (SSRIs; e.g., paroxetine, fluoxetine, citalopram)
  • thiazide diuretics (e.g., hydrochlorothiazide, indapamide)
  • tiotropium
  • tolcapone
  • tolterodine
  • tricyclic antidepressants (e.g., amitriptyline, desipramine, imipramine)
  • zopiclone

Pregnancy Category

TGA pregnancy category – C
FDA pregnancy category – N (Not assigned )


This medication should not be used during pregnancy unless the benefits outweigh the risks. If you become pregnant while taking this medication, contact your doctor immediately.


This medication passes into breast milk. If you are a breast-feeding mother and are taking pentazocine, it may affect your baby. Talk to your doctor about whether you should continue breastfeeding. The safety and effectiveness of using this medication have not been established for children. Accidental ingestion of this medication by children may lead to severe and even f



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