How does this medication work? What will it do for me?

Pentazocine belongs to the class of medications called narcotic analgesics (pain relievers). It is used for the relief of chronic or acute pain of moderate to severe degree. It works by affecting the central nervous system.

Your doctor may have suggested this medication for conditions other than those listed in these drug information articles. As well, some forms of this medication may not be used for all of the conditions discussed here. If you have not discussed this with your doctor or are not sure why you are being given this medication, speak to your doctor. Do not stop taking this medication without consulting your doctor.

Do not give this medication to anyone else, even if they have the same symptoms as you do. It can be harmful for people to take this medication if their doctor has not prescribed it.

What form(s) does this medication come in?

Each mL contains pentazocine 30 mg as pentazocine lactate. Nonmedicinal ingredients: sodium chloride in water for injection; lactic acid, and sodium hydroxide added to adjust for pH.

How should I use this medication?

The usual adult starting dose of pentazocine tablets is 50 mg every 4 hours after meals when required. Dosage is adjusted by the doctor based on response and side effects to 100 mg every 3 to 4 hours.

The injectable is usually given in a hospital setting. It may be injected under the skin, into a muscle, or into a vein. The dose varies according to needs.

Many things can affect the dose of a medication that a person needs, such as body weight, other medical conditions, and other medications. If your doctor has recommended a dose different from the ones listed here, do not change the way that you are taking the medication without consulting your doctor.

This medication may be habit-forming if taken for long periods of time. Do not stop taking this medication without talking with your doctor. If this medication is stopped suddenly, you may experience withdrawal symptoms such as anxiety, sweating, trouble sleeping, shakiness, nausea, tremors, diarrhea, or hallucinations. If you plan on stopping the medication, your doctor may want you to reduce the dose gradually to reduce the severity of withdrawal effects.

It is important to take this medication exactly as prescribed by your doctor. If your doctor has told you to take this medication on a regular basis and you miss a dose, take it as soon as possible and continue with your regular schedule. If it is almost time for your next dose, skip the missed dose and continue with your regular dosing schedule. Do not take a double dose to make up for a missed one. If you are not sure what to do after missing a dose, contact your doctor or pharmacist for advice.

This medication is available under multiple brand names and/or in several different forms. Any specific brand name of this medication may not be available in all of the forms listed here. The forms available for the specific brand you have searched are listed under "What form(s) does this medication come in?"

Do not dispose of medications in wastewater (e.g. down the sink or in the toilet) or in household garbage. Ask your pharmacist how to dispose of medications that are no longer needed or have expired.

Who should NOT take this medication?

Pentazocine should not be taken by anyone who is allergic to pentazocine or to any of the ingredients of the medication.

What side effects are possible with this medication?

Many medications can cause side effects. A side effect is an unwanted response to a medication when it is taken in normal doses. Side effects can be mild or severe, temporary or permanent. The side effects listed below are not experienced by everyone who takes this medication. If you are concerned about side effects, discuss the risks and benefits of this medication with your doctor.

The following side effects have been reported by at least 1% of people taking this medication. Many of these side effects can be managed, and some may go away on their own over time.

Contact your doctor if you experience these side effects and they are severe or bothersome. Your pharmacist may be able to advise you on managing side effects.

  • blurred or double-vision or other changes in vision
  • confusion
  • constipation
  • diarrhea
  • dizziness, lightheadedness, or feeling faint
  • dry mouth
  • drowsiness
  • false sense of well-being
  • headache
  • loss of appetite
  • nausea or vomiting
  • nightmares or unusual dreams
  • redness, swelling, pain, or burning at place of injection (applies to injectable form of medication only)
  • stomach cramps or pain
  • trouble sleeping
  • unusual tiredness or weakness

Although most of these side effects listed below don't happen very often, they could lead to serious problems if you do not check with your doctor or seek medical attention.

Check with your doctor as soon as possible if any of the following side effects occur:

  • feelings of disassociation from reality
  • hallucinations
  • increased sweating
  • redness or flushing of face
  • ringing or buzzing in the ears
  • signs of allergic reaction such as hives, itching, or skin rash
  • symptoms of urinary retention such as decrease in amount of urine, or difficult or painful urination
  • trembling or uncontrolled muscle movements
  • unusual excitement or restlessness (especially in children)

Stop taking the medication and seek immediate medical attention if any of the following occur:

  • confusion
  • dizziness (severe)
  • drowsiness (severe)
  • low blood pressure
  • nervousness or restlessness (severe)
  • signs of a serious allergic reaction (e.g., abdominal cramps, difficulty breathing, nausea and vomiting, or swelling of the face and throat)
  • signs of a severe skin reaction (e.g., blistering, peeling, a rash covering a large area of the body, a rash that spreads quickly, or a rash combined with fever or discomfort)
  • signs of breathing problems (e.g., shallow, irregular breathing, or slow or troubled breathing)
  • signs of taking too much medication (overdose; e.g., cold, clammy skin, pinpoint-sized pupils of eyes, slow heartbeat, or seizures)
  • weakness (severe)

Some people may experience side effects other than those listed. Check with your doctor if you notice any symptom that worries you while you are taking this medication.

Are there any other precautions or warnings for this medication?

Before you begin using a medication, be sure to inform your doctor of any medical conditions or allergies you may have, any medications you are taking, whether you are pregnant or breast-feeding, and any other significant facts about your health. These factors may affect how you should use this medication.

Abdominal conditions: Pentazocine may make the diagnosis of abdominal conditions more difficult or it may worsen these conditions. People with abdominal conditions such as inflammatory or obstructive bowel disease, acute cholecystitis, pancreatitis should discuss with their doctor how this medication may affect their medical condition, how their medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Breathing: This medication can suppress breathing. People at risk for breathing difficulties, such as asthma, should discuss with their doctor how this medication may affect their medical condition, how their medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Dependence and withdrawal: Physical dependence, psychological dependence, and abuse have occurred with the use of pentazocine. People with a history of past or current substance use problems may be at greater risk of developing abuse or addiction while taking this medication. Abuse is not a problem with people who require this medication for pain relief. If this medication is stopped suddenly, you may experience withdrawal symptoms such as anxiety, sweating, trouble sleeping, shaking, pain, nausea, tremors, diarrhea, and hallucinations. If you have been taking this medication for a while, it should be stopped gradually as directed by your doctor.

Drowsiness/reduced alertness: This medication may cause drowsiness. Do not drive, operate machinery, or perform other potentially hazardous tasks until you have determined how this medication affects you.

Head injury: People with head injuries or increased pressure in the head may have a higher risk of experiencing side effects (breathing problems) or worsening of their condition while taking this medication. These people should discuss with their doctor how this medication may affect their medical condition, how their medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Heart disease: Pentazocine may increase blood pressure and cause increased work for the heart. People with high blood pressure or heart disease should discuss with their doctor how this medication may affect their medical condition, how their medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Kidney function: People with kidney disease or reduced kidney function should discuss with their doctor how this medication may affect their medical condition, how their medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Liver function: People with liver disease or reduced liver function should discuss with their doctor how this medication may affect their medical condition, how their medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Other medical conditions: People about to undergo surgery of the biliary tract should use caution while taking pentazocine as it may worsen their condition. Pentazocine will worsen the effects of acute alcohol intoxication and delirium tremens.

As well, people with low thyroid (hypothyroidism), Addison's disease, benign prostatic hypertrophy (enlarged prostate), urethral stricture, decreased function of the adrenal glands, or porphyria should discuss with their doctor how this medication may affect their medical condition, how their medical condition may affect the dosing and effectiveness of this medication, and whether any special monitoring is needed.

Seizures: This medication may cause seizures, especially when higher doses are used or when taken with other medications that may increase the risk of seizures such as:

  • cyclobenzaprine
  • monoamine oxidase inhibitors (MAOIs; e.g., phenelzine, tranylcypromine)
  • neuroleptics (e.g., haloperidol, quetiapine, olanzapine, resperidone)
  • opioids (e.g., morphine, codeine, oxycodone)
  • promethazine
  • selective serotonin reuptake inhibitors (SSRIs; e.g., paroxetine, fluoxetine, citalopram)
  • tricyclic antidepressants (TCAs; e.g., amitriptyline, imipramine)

The risk of seizures is also higher for people with epilepsy, a history of seizures, or who are at risk of seizures (e.g., people with head trauma).

Pregnancy: 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.

Breast-feeding: 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 breast-feeding.

Children: The safety and effectiveness of using this medication have not been established for children.

What other drugs could interact with this medication?

There may be an interaction between pentazocine and any of the following:

  • alcohol
  • anaesthetics
  • antihistamines (e.g., cetirizine, dimenhydrinate, diphenhydramine, hydroxyzine)
  • antipsychotic medications (e.g., olanzepine, quetiapine, risperidone)
  • baclofen
  • barbiturates (e.g., phenobarbital, secobarbital)
  • bupropion
  • buspirone
  • cyclobenzaprine
  • dantrolene
  • desmopressin
  • dextroamphetamine
  • diamorphine
  • diphenoxylate
  • heroin
  • monoamine oxidase inhibitors (e.g, tranylcypromine, phenelzine, moclobemide) taken within the past 14 days
  • octreotide
  • other narcotic analgesics (e.g., codeine, morphine)
  • phenothiazines (e.g., perphenazine, thioridazine)
  • naloxone
  • 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)
  • tobacco (smoking)
  • tricyclic antidepressants (e.g., amitriptyline, desipramine, imipramine)
  • zopiclone

If you are taking any of these medications, speak with your doctor or pharmacist. Depending on your specific circumstances, your doctor may want you to:

  • stop taking one of the medications,
  • change one of the medications to another,
  • change how you are taking one or both of the medications, or
  • leave everything as is.

An interaction between two medications does not always mean that you must stop taking one of them. Speak to your doctor about how any drug interactions are being managed or should be managed.

Medications other than those listed above may interact with this medication. Tell your doctor or prescriber about all prescription, over-the-counter (non-prescription), and herbal medications you are taking. Also tell them about any supplements you take. Since caffeine, alcohol, the nicotine from cigarettes, or street drugs can affect the action of many medications, you should let your prescriber know if you use them.