Diamorphine

Introduction

Diamorphine is a more potent opioid analgesic than morphine. It is used for the relief of severe pain especially in palliative care.

Generic Name 藥名	HA Code 藥物代碼	Classification藥物分類
Diamorphine		DD

Equivalent doses of opioid analgesics

Analgesic/Route	Dose
Codeine: PO	100 mg
Diamorphine: IM, IV, SC	3 mg
Dihydrocodeine: PO	100 mg
Morphine: PO	10 mg
Morphine: IM, IV, SC	5 mg
Oxycodone: PO	6.6 mg
Tramadol: PO	100 mg

Route of Administration : IV

Dosage

For severe acute pain:

Subcutaneous or intramuscular: 5 to 10 mg every 4 hours.

For the pain of myocardial infarction

Slow intravenous: doses of 5mg are given at a rate of 1 to 2 mg/minute with a further dose of 2.5 to 5 mg if required.

For chronic severe pain:

Subcutaneous or intramuscular: 5 to 10 mg every 4 hours; the dose may be increased according to needs.

Administration in children

Doses according to age or body-weight, and adjusted according to response:

By intravenous injection:

• 1 to 2 months: 20 micrograms/kg every 6 hours
• 3 to 5 months: 25 to 50 micrograms/kg every 6 hours
• 6 to 11 months: 75 micrograms/kg every 4 hours
• 1 to 11 years: 75 to 100 micrograms/kg (maximum of 5 mg) every 4 hours

Side Effects

As for Opioid Analgesic in general

The commonest adverse effects are nausea, vomiting, constipation, drowsiness and confusion.

Large doses of opioids produce respiratory depression and hypotension, with circulatory failure and deepening coma. Death may occur from respiratory failure.

Treatment of Adverse Effects

1. Constipation can be treated with laxatives such as senna tables and lactulose.

2. Nausea and vomiting can be alleviated by metoclopramide.

3. Intensive supportive therapy may be required to correct respiratory failure and shock. Naloxone is used for rapid reversal of the severe respiratory depression and coma.

Euphoria, nausea and vomiting, respiratory depression, constipation and cough suppression.

Pharmacokinetics

Oral bioavailability	Diamorphine hydrochloride is well absorbed after subcutaneous or intramuscular injection.It readily crosses the blood-brain barrier.
Onset of action
Metabolism	It is mainly excreted in the urine.
Elimination half-life

Drug Management

Efficiency: Relief of moderate to severe pain, especially that associated with cancer, myocardial infarction and surgery.

Contraindication:

• acute respiratory depression and obstructive airways disease
• acute alcoholism
• convulsive disorders
• head injuries
• avoid in patients at risk of paralytic ileus
• patients with hypothyroidism
• patients with adrenocortical insufficiency
• renal or hepatic impairment
• prostatic hyperplasia

Drowsiness may affect the ability to perform skilled tasks; those so affected should not drive or operate machinery. Morphine should be stopped gradually in patients who may have developed physical dependence, to avoid precipitating withdrawal symptoms (see Dependence )

Abrupt withdrawal of opioids precipitates a withdrawal syndrome. With morphine and diamorphine, withdrawal symptoms usually begin within a few hours, reach a peak within 36 to 72 hours, and then gradually subside; they develop more slowly with methadone.

Withdrawal symptoms include yawning, mydriasis, rhinorrhea, sneezing, muscle tremor, weakness, sweating, nausea vomiting, diarrhoea, bone pain, abdominal and muscle cramps, increases in heart rate, respiratory rate, blood pressure and temperature.

Safety: mental status, blood pressure, respiratory drive, and misuse/overuse.

Caution: Toxic psychosis, CNS depression, severe, cor pulmonale Tolerance and dependence

Contraindication: where hepatic and renal impairment may result in toxicity