Pentazo

Indications

Pentazocine is an opioid painkiller used for moderate to severe pain, such as pain after surgery, injuries, kidney or gallstone colic, and in labour. The injection is also used before and during anaesthesia.

How It Works

Pentazocine acts on opioid receptors in the brain and spinal cord. It mainly stimulates kappa receptors and partly blocks mu receptors (a mixed agonist-antagonist). This changes how pain signals are felt and reduces pain, with a ceiling on breathing depression compared with stronger opioids.

Dosage and Administration

Injection: given into a muscle, under the skin or into a vein by a doctor or nurse, as prescribed. Tablets: take as prescribed, usually every 3 to 4 hours as needed, with food or water, using the lowest dose for the shortest time. Do not increase the dose or use it longer than prescribed. Do not stop suddenly after long use.

Interactions

• Alcohol, benzodiazepines such as Diazepam, sleeping pills, antihistamines and other opioids increase drowsiness and the risk of slowed breathing.
• It can cause withdrawal symptoms in people dependent on Morphine, Heroin, Methadone or other opioids.
• MAO inhibitors and some antidepressants can cause serious reactions.
• Smoking may increase how fast it is cleared from the body.

Contraindications

• Allergy to pentazocine.
• Severe breathing problems, acute severe asthma, or a head injury or raised pressure in the skull.
• Recent heart attack, severe high blood pressure, heart failure from lung disease.
• Porphyria, and dependence on other opioids.

Side Effects

Common: dizziness, drowsiness, nausea, vomiting, sweating and light-headedness. Others: confusion, strange dreams, hallucinations, mood changes, raised blood pressure and heart rate, constipation, and pain or skin damage at repeated injection sites. Dependence and misuse can occur.

Get urgent medical help for slow or shallow breathing, extreme sleepiness or inability to wake, severe confusion or hallucinations, chest pain, fits, or a severe allergic reaction.

Pregnancy and Lactation

Use in pregnancy only if clearly needed and as directed by the doctor. Regular use late in pregnancy can cause withdrawal in the newborn, and use in labour can affect the baby's breathing. Small amounts pass into breast milk; a single dose is usually acceptable, but regular use while breastfeeding should be avoided.

Precautions and Warnings

• Do not drive or operate machines if drowsy or dizzy.
• Use with care in liver or kidney disease, older people, and those with a history of drug misuse.
• Keep securely and never share with others.

Overdose

Overdose can cause severe drowsiness, slowed breathing, low blood pressure, fits, coma and death. Get emergency help immediately; Naloxone can reverse the effects.

Therapeutic Class

Opioid analgesic (mixed agonist-antagonist).

Storage

Store below 30°C in a dry place, away from light, and out of the reach of children. Injections are stored as directed on the pack.