Pethidine-R

Indications

Pethidine Hydrochloride is a strong opioid painkiller, given mainly by injection. It is used for short-term relief of moderate to severe pain, such as pain during labour, after surgery or from injuries, and before or during anaesthesia. Because of its side effects and short action, it is not suitable for long-term pain. It is a controlled medicine used under close medical supervision.

How It Works

Pethidine attaches to opioid receptors in the brain and spinal cord. This reduces the way pain signals are sent and felt, and changes the emotional response to pain. It also causes sedation. Its effect starts quickly and lasts a few hours.

Dosage and Administration

Pethidine injection is given by a doctor, nurse or midwife, into a muscle, under the skin or slowly into a vein, at a dose decided for each patient according to the type of pain, age, weight and kidney function. Repeat doses and the total daily amount are limited and supervised. It should be used only for short periods. Older people and those with kidney or liver problems need lower doses.

Interactions

• MAO inhibitors (such as Selegiline or Moclobemide), including use within the last 14 days, can cause a severe, sometimes fatal reaction: Pethidine must not be given.
• Benzodiazepines (such as Diazepam), sleeping pills, other opioids, Gabapentin, Pregabalin, alcohol and sedating antihistamines can cause deep sedation, slowed breathing, coma and death.
• SSRIs, SNRIs, Tramadol, Linezolid and triptans increase the risk of serotonin syndrome.
• Ritonavir, Phenytoin and Carbamazepine can increase the build-up of a toxic breakdown product (norpethidine).
• Metoclopramide and anticholinergic drugs may change its effect on the gut.

Contraindications

• Allergy to Pethidine.
• Severe breathing difficulty, acute asthma attack or severe lung disease.
• Use of an MAO inhibitor now or in the last 14 days.
• Head injury or raised pressure inside the skull.
• Severe kidney impairment, acute alcohol intoxication, bowel paralysis (paralytic ileus) or seizure disorders not under control.

Side Effects

Common side effects include drowsiness, dizziness, nausea and vomiting, sweating, dry mouth, flushing, constipation and light-headedness on standing.

Serious effects include slow or shallow breathing, low blood pressure, slow or fast heartbeat, confusion, tremor, muscle twitching and fits (more likely with repeated doses or kidney problems), and allergic reactions. Repeated use can lead to tolerance, dependence and withdrawal symptoms.

Get urgent medical help, or alert the nurse straight away, if breathing becomes slow or shallow, the person is very hard to wake, has blue lips, a fit, fainting, a severe rash or swelling of the face and throat.

Pregnancy and Lactation

Pethidine is sometimes used for pain relief in labour. It crosses the placenta and can make the newborn drowsy and slow to breathe, and may affect early breastfeeding; staff monitor the baby and can give an antidote if needed. Regular use during pregnancy can cause withdrawal in the newborn. It passes into breast milk and its breakdown product can build up in the baby, so other painkillers are usually preferred when breastfeeding; the doctor will advise.

Precautions and Warnings

Doctors use it carefully in older people and in those with breathing problems, sleep apnoea, low blood pressure, thyroid or adrenal problems, enlarged prostate, liver or kidney disease, epilepsy, inflammatory bowel disease or a history of substance misuse. Do not drink alcohol. Do not drive or operate machinery after receiving it. It can be habit-forming and is a controlled drug.

Overdose

Overdose causes pinpoint pupils, severe drowsiness, very slow breathing, low blood pressure, fits and coma, and can be fatal. It is an emergency: the opioid antidote Naloxone is given along with breathing support in hospital.

Therapeutic Class

Opioid analgesic (phenylpiperidine derivative); controlled drug.

Storage

Hospital medicine and controlled drug: store as directed on the pack, usually below 30°C, protected from light, in a locked cabinet and out of the reach of children. Do not freeze.