Naloxone / Pentazocine Side Effects

Medically reviewed by Drugs.com. Last updated on Mar 2, 2025.

Applies to naloxone / pentazocine: oral tablet.

Important warnings This medicine can cause some serious health issues

Oral route (tablet)

Addiction, Abuse, and Misuse

Pentazocine and naloxone tablets expose patients and other users to the risks of opioid addiction, abuse, and misuse, which can lead to overdose and death.

Assess each patient's risk prior to prescribing pentazocine and naloxone tablets, and monitor all patients regularly for the development of these behaviors or conditions.

Opioid Analgesic Risk Evaluation and Mitigation Strategy (REMS)

To ensure that the benefits of opioid analgesics outweigh the risks of addiction, abuse, and misuse, the Food and Drug Administration (FDA has required a REMS for these products.

Under the requirements of the REMS, drug companies with approved opioid analgesic products must make REMS-compliant eduction programs available to healthcare providers.

Healthcare providers are strongly encouraged to complete a REMS-compliant education program, counsel patients and/or their caregivers, with every prescription, on safe use, serious risks, storage, and disposal of these products, emphasize to patients and their caregivers the importance of reading the Medication Guide every time it is provided by their pharmacist, and consider other tools to improve patient, household, and community safety.

Life-Threatening Respiratory Depression

Serious, life-threatening, or fatal respiratory depression may occur with use of pentazocine and naloxone tablets.

Monitor for respiratory depression, especially during initiation of pentazocine and naloxone tablets or following a dose increase.

Accidental Ingestion

Accidental ingestion of even one dose of pentazocine and naloxone tablets, especially by children, can result in a fatal overdose of pentazocine.

Neonatal Opioid Withdrawal Syndrome

Prolonged use of pentazocine and naloxone tablets during pregnancy can result in neonatal opioid withdrawal syndrome, which may be life-threatening if not recognized and treated, and requires management according to protocols developed by neonatology experts.

If opioid use is required for a prolonged period in a pregnant woman, advise the patient of the risk of neonatal opioid withdrawal syndrome and ensure that appropriate treatment will be available.

Risks from Concomitant Use with Benzodiazepines or Other CNS Depressants

Concomitant use of opioids with benzodiazepines or other CNS depressants, including alcohol, may result in profound sedation, respiratory depression, coma, and death.

Reserve concomitant prescribing of pentazocine and naloxone tablets or other CNS depressants for use in patients for whom alternative treatment options are inadequate.

Limit dosages and durations to the minimum required.

Follow patients for signs and symptoms of respiratory depression and sedation.

Serious side effects

Along with its needed effects, naloxone / 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 immediately if any of the following side effects occur while taking naloxone / pentazocine:

Rare side effects

• black, tarry stools
• chest pain
• chills
• cough
• difficult or troubled breathing
• fever
• general feeling of tiredness or weakness
• hoarseness
• irregular, fast or slow, or shallow breathing
• lower back or side pain
• painful or difficult urination
• pale or blue lips, fingernails, or skin
• shakiness in the legs, arms, hands, or feet
• sore throat
• sores, ulcers, or white spots on the lips or in the mouth
• swollen glands
• trembling or shaking of the hands or feet
• unusual bleeding or bruising
• unusual tiredness or weakness

Incidence not known

• agitation
• blistering, peeling, or loosening of the skin
• blurred vision
• burning, crawling, itching, numbness, prickling, "pins and needles", or tingling feelings
• confusion
• constipation
• constricted, pinpoint, or small pupils (black part of the eye)
• darkening of the skin
• decrease in the frequency of urination
• depression
• diarrhea
• difficulty in passing urine (dribbling)
• difficulty with swallowing
• dizziness
• dizziness, faintness, or lightheadedness when getting up suddenly from a lying or sitting position
• excitement
• fainting
• false or unusual sense of well-being
• fast, slow, pounding, or irregular heartbeat or pulse
• feeling of warmth
• headache
• hives or welts, itching, skin rash
• joint or muscle pain
• loss of bladder control
• loss of consciousness
• nervousness
• overactive reflexes
• poor coordination
• pounding in the ears
• puffiness or swelling of the eyelids or around the eyes, face, lips, or tongue
• rapid breathing
• red skin lesions, often with a purple center
• red, irritated eyes
• redness of the face, neck, arms, and occasionally, upper chest
• restlessness
• sweating
• swelling of the face, arms, or lower legs
• tightness in the chest
• total body jerking
• upper abdominal or stomach pain
• weight gain

Get emergency help immediately if any of the following symptoms of overdose occur while taking naloxone / pentazocine:

Symptoms of overdose

• chest pain
• choking
• cold and clammy skin
• constricted, pinpoint, or small pupils (black part of the eye)
• coughing that sometimes produces a pink frothy sputum
• decreased awareness or responsiveness
• difficult, fast, or noisy breathing
• extremely shallow or slow breathing
• increased sweating
• loss of consciousness
• no muscle tone or movement
• pale skin
• seeing, hearing, or feeling things that are not there
• severe sleepiness or unusual drowsiness
• seizures (convulsions)
• slow heartbeat
• swelling in the legs and ankles

Other side effects

Some side effects of naloxone / 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:

Rare side effects

• stomach distress

Incidence not known

• continuing ringing or buzzing or other unexplained noise in the ears
• cracked, dry, or scaly skin
• difficulty in focusing the eyes
• disturbed dreams
• drowsiness
• dry mouth
• hearing loss
• irritability
• lightheadedness
• loss of appetite
• mood or mental changes
• nausea
• relaxed and calm feeling
• trouble with sleeping
• vomiting
• weakness
• weight loss

For healthcare professionals

Applies to naloxone / pentazocine: oral tablet.

General adverse events

The most commonly occurring adverse reactions have included nausea, dizziness, lightheadedness, vomiting, and euphoria.^[Ref]

Respiratory

• Postmarketing reports: Respiratory depression

Psychiatric

• Postmarketing reports: Hallucinations (usually visual), confusion, disorientation, depression, euphoria, disturbed dreams, insomnia, irritability, excitement, irritability

Hypersensitivity

• Postmarketing reports: Anaphylaxis, facial edema, rash

Cardiovascular

• Postmarketing reports: Hypertension, hypotension, circulatory depression, tachycardia, syncope

A 45-year-old male narcotic addict and alcoholic with hepatitis and undiscovered cardiomyopathy was given 0.8 mg of naloxone intravenously over a 2 minute period and developed ventricular fibrillation. The patient required naloxone once more for this episode and again developed ventricular fibrillation. A second opioid overdose in the same patient was treated with an initial dose of 0.4 mg intravenously, followed by 0.4 mg intravenously, then intramuscularly. Each time the patient developed ventricular fibrillation responsive to cardioversion and/or lidocaine.

Severe hypertension (mean arterial pressure rising from a baseline of 107 mmHg to 147 mmHg in about 2 to 3 hours) has been reported in an essential hypertension patient given an initial 8 mg dose of naloxone intravenously, followed by an infusion of 0.13 mg/min over the next 2.5 hours. When the naloxone was discontinued the blood pressure quickly returned to normal.

Mild hypotension and one case of moderate hypertension were observed in patients receiving a bolus dose of 4 mg/kg of naloxone followed by 2 mg/kg/hour for 24 hours. One study reported that the newborn infants of mothers who have received naloxone near term may experience tachycardia.

Gastrointestinal

• Postmarketing reports: Nausea, vomiting, constipation, diarrhea, anorexia, biliary tract spasms, dry mouth, abdominal distress

Dermatologic

• Postmarketing reports: Sweating, flushed skin, dermatitis, pruritus, rash, urticaria, serous skin reactions including erythema multiforme, Stevens-Johnson syndrome, toxic epidermal necrolysis

Other

• Postmarketing reports: Tinnitus, chills

Withdrawal syndromes from the use of naloxone may be precipitated by as little as 0.05 to 0.2 mg intravenously in patients taking 24 mg per day of methadone.

Ocular

• Postmarketing reports: Visual blurring and focusing difficulty, blurred vision, diplopia, miosis, nystagmus

Genitourinary

• Postmarketing reports: Urinary retention, alteration in rate or strength of labor contractions

Hematologic

• Postmarketing reports: Depression of the white blood cell count (especially granulocytes), moderate transient eosinophilia, agranulocytosis

Depression of the white blood cell count is usually reversible.

Endocrine

Opioids:

• 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.

Further information

Naloxone/pentazocine side effects can vary depending on the individual. Always consult your healthcare provider to ensure the information displayed on this page applies to your personal circumstances.

Note: Medication side effects may be underreported. If you are experiencing side effects that are not listed, submit a report to the FDA by following this guide.

Medical Disclaimer