Dosage should be individualised. Some of the factors to be considered in determining the dose are: age, body weight, physical status, underlying pathological condition, use of other medicines, type of anaesthesia to be used, and the surgical procedure involved. The initial dose should be reduced in the elderly and in debilitated patients. The effect of the initial dose should be taken into account in determining supplemental doses. Vital signs should be monitored routinely.
Usual Dosage in Adult: Premedication (To be appropriately modified in the elderly, debilitated and those who have received other depressant medicines) 50 to 100 micrograms (1 to 2 ml) may be administered intramuscularly 30 to 60 minutes prior to surgery. Adjunct to general anaethesia: Induction – 50 to 100 micrograms (1 to 2 ml) may be administered initially intravenously and may be repeated at 2 to 3 minute intervals until the desired effect is achieved. A reduced dose as low as 25 to 50 micrograms (0.5 to 1 mL) is recommended in elderly and poor-risk patients. Maintenance – 25 to 50 micrograms (0.5 to 1 ml) may be administered intravenously or intramuscularly when movement and/or changes in vital signs indicate surgical stress or lightening of analgesia.
Adjunct to regional anaesthesia: 50 to 100 micrograms (1 to 2 ml) may be administered intramuscularly or slowly intravenously when additional analgesia is required. Post-operatively – (Recovery room): 50 to 100 micrograms (1 to 2 ml) may be administered intramuscularly for the control of pain, tachypnoea, and emergence delirium.The dose may be repeated in one or two hours as needed.
Usual Dosage in Children: For induction and maintenance in children 2-12 years of age, a reduced dose as low as 20 to 30 micrograms (0.4 to 0.6 ml) per 10 kg is recommended.