Skip to Content

Pentazocine Side Effects

For the Consumer

Applies to pentazocine: injection solution

Along with its needed effects, pentazocine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor or nurse immediately if any of the following side effects occur while taking pentazocine:

  • Black, tarry stools
  • blistering, peeling, or loosening of the skin
  • chest pain
  • chills
  • cough
  • diarrhea
  • fast, pounding, or irregular heartbeat or pulse
  • fever
  • itching
  • joint or muscle pain
  • painful or difficult urination
  • red, irritated eyes
  • red skin lesions, often with a purple center
  • shakiness in the legs, arms, hands, or feet
  • sore throat
  • sores, ulcers, or white spots on the lips or in the mouth
  • swelling or puffiness of the face
  • swollen glands
  • trembling or shaking of the hands or feet
  • trouble breathing
  • unusual bleeding or bruising
  • unusual tiredness or weakness
Incidence not known
  • 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
  • decrease in the frequency of urination
  • 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
  • pale or blue lips, fingernails, or skin
  • pounding in the ears
  • rapid breathing
  • small lumps under the skin at the injection site
  • stinging at the injection site
  • sweating
  • swelling of the lower legs or arms
  • tightness in the chest
  • very slow breathing
  • weight gain

Some side effects of pentazocine may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

More common Rare
  • 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
Incidence not known
  • Continuing ringing or buzzing or other unexplained noise in the ears
  • difficulty having a bowel movement (stool)
  • difficulty in focusing the eyes
  • disturbed dreams
  • drowsiness
  • dry mouth
  • excitement
  • hearing loss
  • irritability
  • relaxed and calm
  • sleepiness
  • trouble sleeping
  • weakness

For Healthcare Professionals

Applies to pentazocine: injectable solution


The most commonly occurring adverse reactions have included nausea, dizziness or lightheadedness, vomiting, and euphoria.


Postmarketing reports: Soft tissue induration, nodules and cutaneous depressions at injection sites; ulceration (sloughing), severe sclerosis of the skin and subcutaneous tissues and, rarely, underlying muscle; diaphoresis, sting on injection, flushed skin including plethora, dermatitis including pruritus[Ref]


Postmarketing reports: Anaphylaxis, facial edema, toxic epidermal necrolysis[Ref]

Nervous system

Serotonin syndrome has been reported during concomitant use of opioids with serotonergic drugs.[Ref]

Postmarketing reports: Dizziness, lightheadedness, sedation, headache, weakness, flushing, syncope, tremor, paresthesia

Postmarketing reports: Serotonin syndrome[Ref]


Postmarketing reports: Depression, euphoria, confusion, disorientation, disturbed dreams, insomnia, irritability, excitement, hallucinations[Ref]


Postmarketing reports: Respiratory depression, dyspnea, transient apnea (in infants whose mothers received this drug during labor)[Ref]


Postmarketing reports: Circulatory depression, shock, hypertension, tachycardia, syncope[Ref]


Postmarketing reports: Nausea, vomiting, constipation, dry mouth, taste alteration, diarrhea and cramps[Ref]


Depression of the white blood cell count is usually reversible.[Ref]

Postmarketing reports: Depression of the white blood cell count (especially granulocytes), moderate transient eosinophilia[Ref]


Postmarketing reports: Tinnitus, chills[Ref]


Postmarketing reports: Visual blurring and focusing difficulty, blurred vision, diplopia, miosis, nystagmus[Ref]


Postmarketing reports: Urinary retention, alteration in rate or strength of labor contractions[Ref]


Postmarketing reports: Adrenal insufficiency, Androgen deficiency

Cases of adrenal insufficiency have been reported with opioid use, generally use greater than 1 month. Cases of androgen deficiency have been reported with chronic opioid use.


1. "Product Information. Talwin NX (pentazocine)." Sanofi Winthrop Pharmaceuticals, New York, NY.

Some side effects of pentazocine may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA.

Disclaimer: Every effort has been made to ensure that the information provided is accurate, up-to-date and complete, but no guarantee is made to that effect. In addition, the drug information contained herein may be time sensitive and should not be utilized as a reference resource beyond the date hereof. This material does not endorse drugs, diagnose patients, or recommend therapy. This information is a reference resource designed as supplement to, and not a substitute for, the expertise, skill , knowledge, and judgement of healthcare practitioners in patient care. The absence of a warning for a given drug or combination thereof in no way should be construed to indicate safety, effectiveness, or appropriateness for any given patient. does not assume any responsibility for any aspect of healthcare administered with the aid of materials provided. The information contained herein is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. If you have questions about the substances you are taking, check with your doctor, nurse, or pharmacist.