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
 

Morphine

Group: opioid analgesic
Injection: 10 mg (sulfate or hydrochloride) in 1-ml ampoule
Oral solution: 10 mg (sulfate or hydrochloride) in 5 ml
Tablet: 10 mg (sulfate or hydrochloride)

General information

Morphine is the principal alkaloid of opium. It is the most potent of the narcotic analgesics and a dangerous drug of addiction. Its supply is controlled under Schedule 1 of the Single Convention on Narcotic Drugs, 1961. It is extensively absorbed following oral administration but parenteral administration produces a more reliable and more rapid response. The plasma half-life is 2-3 hours. It is largely metabolized in the liver and subsequently excreted in the urine.

Clinical information

Uses

• Preoperative management of musculoskeletal and visceral pain.

• Premedication prior to general surgery.

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

• Postoperative analgesia.

Dosage and administration

Premedication

Adults: 150-200 micrograms/kg i.m. or subcutaneously 1 hour before operation.
Children: 50-100 micrograms/kg as above, to a maximum of 10 mg.

Preoperative analgesia

Adults: 150-200 micrograms/kg i.m. or i.v.
Children: 50-100 micrograms/kg i.m.

During anaesthesia

Adults and children: 100 micrograms/kg i.v. repeated every 40-60 minutes as required.

Postoperative analgesia

Adults: 150-300 micrograms/kg i.m. every 4 hours or, by continuous intravenous infusion, 8-10 mg in 30 minutes, then 2-2.5 mg/hour.

Children: 100-200 micrograms/kg i.m. or subcutaneously repeated as necessary. No more than 10 mg should be administered as a single dose.

Rarely, morphine is administered by epidural or intrathecal injection to provide postoperative analgesia. These procedures should be attempted only by experienced specialist anaesthetists and must be used only when facilities for close monitoring of the patient are available. The preparations used must be free of preservatives.

Morphine should be administered at reduced dosage to patients who are elderly or who have cardiorespiratory disease or renal insufficiency.

Contraindications

• 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.

• Diverticulitis and other spastic conditions of the colon, biliary colic and recent surgery on the biliary tract.

• Use of monoamine oxidase inhibitors within the previous 14 days.

Precautions

Vital signs must be monitored regularly in the immediate postoperative period when morphine is administered during anaesthesia since respiratory depression may persist for several hours. In addition, marked respiratory depression may occur up to several hours after epidural administration. Facilities for intermittent positive pressure ventilation must therefore 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

Morphine 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

Acute dose-related effects include respiratory depression; anorexia, nausea, vomiting and constipation; euphoria, dizziness, drowsiness and confusion; dry mouth and spasm of the urinary and biliary tract; hypotension, bradycardia and palpitations.

Allergic phenomena are uncommon but anaphylactoid reactions have been reported.

Prolonged administration may result in physical dependence.

Drug interactions

Morphine 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 morphine since they may cause restlessness or confusion.

Overdosage

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.

Storage

Morphine tablets, solution and injection should be kept in tightly closed containers 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

1 Single convention on narcotic drugs, 1961. New York, United Nations, 1997.

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