Indications: supplementation of general anaesthesia during induction and analgesia during maintenance of anaesthesia ( for use in patients undergoing cardiac surgery); analgesia and sedation in ventilated, intensive care patients.

Cautions: in head injuries with increased intracranial pressure; in patients with chronic respiratory insufficiency.

Contra-indications: left ventricular dysfunction; avoid in acute respiratory depression, acute alcoholism and where risk of paralytic ileus; avoid injection in pheochromocytoma.

Side Effects: nausea and vomiting (particularly in initial stages), constipation, and drowsiness; larger doses produce respiratory depression, hypotension, and muscle rigidity; other side effects: include difficulty with micturition, ureteric or biliary spasm, dry mouth, sweating, headache, facial flushing, vertigo, bradycardia, tachycardia, palpitation, postural hypotension, hypothermia, hallucinations, dysphoria, mood changes, dependence, miosis, decreased libido or potency, rashes, urticaria and pruritus; hypertension, hypoxia; very rarely asystole and anaphylaxis.

Dose: Induction of anaesthesia, adult and child over 12 years, by intravenous infusion, 0.5–1 mcg/kg/minute, with or without an initial dose by intravenous injection of 0.25–1 mcg/kg over at least 30 seconds. Maintenance of anaesthesia in ventilated patients, adult and child over 12 years, by intravenous infusion, 0.05–2mcg/kg/minute (with or without an initial dose by intravenous injection of 0.25–1 mcg/kg over at least 30 seconds) according to anaesthetic technique and adjusted according to response; in light anaesthesia supplemental doses by intravenous injection every 2–5 minutes.

Maintenance of anaesthesia in spontaneous respiration anaesthesia, adult and child over 12 years, by intravenous infusion, initially 40 nanograms/kg/minute adjusted according to response, usual range 25–100 nanograms/kg/minute.

Maintenance of anaesthesia, child 1–12 years, by intravenous infusion, 0.05–1.3 mcg/kg/minute (with or without an initial dose by intravenous injection of 0.1–1 mcg/kg over at least 30 seconds) according to anaesthetic technique and adjusted according to response.

Analgesia and sedation in ventilated, intensive care patients, by intravenous infusion, adult over 18 years initially 100–150 nanograms/kg/minute adjusted according to response in steps of 25 nanograms/kg/minute (allow at least 5 minutes between dose adjustments); usual range 6–740 nanograms/kg/minute; if an infusion rate of 200 nanograms/kg/minute does not produce adequate sedation add another sedative.

Additional analgesia during stimulating or painful procedures in ventilated, intensive care patients, by intravenous infusion, adult over 18 years maintain infusion rate of at least 100 nanograms/kg/minute for at least 5 minutes before procedure and adjust every 2–5 minutes according to requirements, usual range 250–750 nanograms/kg/minute.