Indications
Pentazocine is an opioid painkiller used for the relief of moderate to severe pain, for example after injuries or surgery, and sometimes as part of pain relief before or during operations. It is generally used for short periods.
How It Works
Pentazocine acts on opioid receptors in the brain and spinal cord. It mainly stimulates kappa opioid receptors, which reduces how pain signals are felt, and partly blocks mu opioid receptors. Because of this mixed action it has a ceiling to its pain-relieving effect and can bring on withdrawal symptoms in people who are dependent on other opioids.
Dosage and Administration
Use only as prescribed. For tablets, the usual adult dose is 50 mg every 3 to 4 hours, increased to 100 mg if needed, not exceeding 600 mg in 24 hours; take after food. Injections are given by a doctor or nurse into a muscle, under the skin or into a vein at a dose set by the doctor. Use the lowest effective dose for the shortest time. Do not stop suddenly after regular use; your doctor will reduce the dose gradually.
Interactions
- Alcohol, Benzodiazepines (such as Diazepam), sleeping tablets, Gabapentin, Pregabalin, antihistamines and other sedatives greatly increase the risk of severe drowsiness, slowed breathing and death.
- It may cause withdrawal in people taking Morphine, Methadone or other strong opioids, and may reduce their pain relief.
- Do not use with, or within 2 weeks of, MAO inhibitors.
- Serotonergic medicines such as SSRIs, Tramadol and Linezolid may increase the risk of serotonin syndrome.
- Smoking may increase the dose needed.
Contraindications
- Severe breathing problems, acute severe asthma or slowed breathing.
- Head injury or raised pressure inside the skull.
- Acute alcohol intoxication.
- Porphyria.
- Heart failure due to lung disease, or recent heart attack (it can raise blood pressure and strain the heart).
- Dependence on other opioids.
- Allergy to Pentazocine.
Side Effects
Common effects include nausea, vomiting, dizziness, drowsiness, sweating, light-headedness, dry mouth and constipation. It can cause unusual mental effects such as confusion, nightmares, strange thoughts, feeling detached or hallucinations, especially at higher doses or in older people. It can raise blood pressure and heart rate. Repeated injections can damage skin and muscle at the injection site. Regular use can lead to tolerance, dependence and addiction.
Get urgent medical help for slow or shallow breathing, extreme sleepiness or difficulty waking, blue lips, chest pain, fainting, a seizure, severe confusion or hallucinations, or signs of allergy such as facial swelling or difficulty breathing.
Pregnancy and Lactation
Avoid in pregnancy unless your doctor decides it is essential. Use near delivery can cause breathing problems in the newborn, and regular use in pregnancy can cause withdrawal symptoms in the baby after birth. Small amounts pass into breast milk; occasional short-term use may be acceptable if your doctor agrees, but watch the baby for unusual sleepiness, poor feeding or breathing problems.
Precautions and Warnings
- Risk of addiction and misuse; keep it secure and never share it.
- Do not drive, operate machinery or drink alcohol while using it.
- Use with care in older people, and in liver or kidney disease, low thyroid, enlarged prostate, epilepsy, low blood pressure, gallbladder disease and lung disease.
- Tell your doctor about any past alcohol or drug dependence.
Overdose
Overdose can cause severe drowsiness, slowed or stopped breathing, low blood pressure, seizures, coma and death. Call for emergency help immediately. Naloxone can reverse the breathing effects but may need repeated doses in hospital.
Therapeutic Class
Opioid analgesic, mixed agonist-antagonist (benzomorphan).
Storage
Store below 30°C in a dry place, away from light and out of the reach of children, in a secure place.
Prepared by the Oshud Alo team from standard drug references. For information only; always follow your doctor's advice.