WHO Model Prescribing Information: Drugs Used in Anaesthesia
(1989; 60 pages) [French] View the PDF document
Table of Contents
View the documentPreface
View the documentIntroduction
Open this folder and view contentsPremedication
Open this folder and view contentsGeneral anaesthetics and oxygen
Open this folder and view contentsLocal anaesthetics
Open this folder and view contentsNon-opioid analgesics
Close this folderOpioid analgesics and antagonists
View the documentMorphine
View the documentPethidine
View the documentNaloxone
Open this folder and view contentsMuscle relaxants and cholinesterase inhibitors
Open this folder and view contentsBlood substitutes
Open this folder and view contentsSolutions for correcting water and electrolyte imbalance
Open this folder and view contentsAntacid for use in obstetric practice
View the documentAnaesthesia at the District Hospital
View the documentSelected WHO publications of related interest
View the documentBack cover


Group: opioid analgesic
Injection: 50 mg (hydrochloride) in 1-ml ampoule
Tablet: 50 mg (hydrochloride)

General information

Pethidine is a synthetic narcotic analgesic that competes for the same receptors as morphine in the central nervous system. It is a dangerous drug of addiction. Its supply is controlled under Schedule I of the Single Convention on Narcotic Drugs, 1961.

Pethidine is comparable to morphine in its sedative and tranquillizing effects, but the analgesia and respiratory depression it produces are of shorter duration, and it induces less smooth muscle spasm. Pethidine is preferred to morphine in the preoperative management of biliary colic and in the management of acute diverticulitis.

It is well absorbed orally but parenteral administration is more effective. Its plasma half-life is about 3 hours. It is largely metabolized in the liver and the end-products are excreted in the urine.

Clinical information


• Preoperative management of musculoskeletal and visceral pain.

• Premedication prior to general anaesthesia.

• An adjunct to inhalational and other anaesthetic agents during major surgical interventions.

• To prevent tachypnoea induced by trichloroethylene.

• Postoperative and obstetric analgesia.

• In combination with diazepam, and in the absence of other agents, for reduction of fractures and other minor interventions.

Dosage and administration


Adults: 50-100 mg i.m. or subcutaneously 1 hour before induction.
Children: 1 mg/kg i.m. or subcutaneously 1 hour before induction.

Preoperative analgesia

Adults: 50-100 mg i.m. or i.v.
Children: 1 mg/kg i.m.

During general anaesthesia

Adults and children: 0.25 mg/kg i.v. repeated every 40-60 minutes as required.

Postoperative analgesia

Adults: 50-150 mg i.m. every 4 hours, or 15-35 mg/hour by continuous intravenous infusion.
Children: 1-2 mg/kg orally, i.m. or subcutaneously, repeated every 4 hours as necessary.

Obstetric analgesia

A dose of 1 mg/kg, repeated as needed. The last dose should be administered, when possible, 1-3 hours prior to delivery in order to prevent neonatal depression.

Dosage should be reduced in elderly patients and those with cardiorespiratory disease.


• Bronchial asthma, emphysema or heart failure secondary to chronic lung disease.
• Increased intracranial pressure, head injury or brain tumour.
• Severe hepatic impairment, adrenocortical insufficiency, hypothyroidism.
• Convulsive disorders, acute alcoholism, delirium tremens.
• Use of monoamine oxidase inhibitors within the previous 14 days.


Vital signs must be monitored regularly in the immediate postoperative period when pethidine has been administered during anaesthesia since respiratory depression may persist for several hours.

Facilities for intermittent positive pressure ventilation must be immediately available.

To reduce risk of dependence, opioids should not normally be used for postoperative analgesia for longer than 7 days.

Use in pregnancy

Pethidine should be used during pregnancy only when the need outweighs any possible risk to the fetus. Its use during labour may produce respiratory depression in the infant, who may require administration of naloxone 10 micrograms/kg i.m. immediately after birth.

Adverse effects

Adverse effects include respiratory depression, nausea and vomiting, dizziness, drowsiness and confusion, hypotension, bradycardia and palpitations.

Allergic phenomena are uncommon but anaphylactoid reactions have been reported.

Physical dependence may occur with prolonged administration.

Drug interactions

Pethidine potentiates the effects of other cerebral depressants. Its effect is counteracted by naloxone within 2 minutes.

Sedatives should be withheld if a patient has been given pethidine since they may cause restlessness or confusion.


Serious overdosage is characterized by respiratory depression, extreme somnolence progressing to stupor or coma, and pin-point pupils. Cardiovascular collapse and cardiac arrest are terminal events. Supportive therapy includes mechanically assisted ventilation and administration of pressor drugs and fluids to maintain the circulating blood volume. Except in dependent individuals, in whom specific opioid antagonists induce an intense acute withdrawal reaction, naloxone (200 micrograms i.v.) should be administered, as necessary, at 2-minute intervals.


Pethidine tablets and injection should be kept in tightly closed containers protected from light, and should not be allowed to freeze.

The requirements relating to drugs controlled under Schedule 1 of the Single Convention on Narcotic Drugs should be observed.1

1Single convention on narcotic drugs, 1961. New York, United Nations, 1977.

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