Fentanyl

SPC §4.2 verbatim adult table — 'Spontaneous Respiration: Initial 50-200 micrograms, Supplemental 50 micrograms. Assisted Ventilation: Initial 300-3500 micrograms, Supplemental 100-200 micrograms. Doses in excess of 200 micrograms are for use in anaesthesia only.' 'The dose of fentanyl should be individualised according to age, body weight, physical status, underlying pathological condition, use of other drugs and type of surgery and anaesthesia.' PREMEDICATION: 'As a premedicant, 1-2 ml fentanyl may be given intramuscularly 45 minutes before induction of anaesthesia' — at the fetched product strength of 50 micrograms/ml that is 50–100 micrograms (arithmetic, from the product name; the SPC states the volume). DURATION: '2 ml fentanyl may be expected to provide sufficient analgesia for 10-20 minutes in surgical procedures involving low pain intensity' (= 100 micrograms); '10 ml fentanyl injected as a bolus gives analgesia lasting about one hour' (= 500 micrograms); 'Giving a dose of 50 micrograms/kg fentanyl will provide intense analgesia for some four to six hours, for intensely stimulating surgery.' INFUSION: 'In ventilated patients, a loading dose of fentanyl may be given as a fast infusion of approximately 1 microgram/kg/min for the first 10 minutes followed by an infusion of approximately 0.1 micrograms/kg/min... Unless it is planned to ventilate post-operatively, the infusion should be terminated at about 40 minutes before the end of surgery. Lower infusion rates, e.g. 0.05-0.08 micrograms/kg/minute are necessary if spontaneous ventilation is to be maintained. Higher infusion rates (up to 3 micrograms/kg/minute) have been used in cardiac surgery.' ELDERLY/DEBILITATED: 'the initial dose should be reduced in the elderly (>65 years of age) and in debilitated patients.' OBESITY: 'In obese patients there is a risk of overdosing if the dose is calculated based on body weight. Obese patients should have dosage calculated according to their estimated lean body mass.' INCOMPATIBILITY: chemically incompatible with pentobarbital sodium, thiopentone and methohexitone. NO MAXIMUM DOSE is stated in either fetched label — the '200 micrograms' figure is a restriction on setting (anaesthesia only), not a stated ceiling, so no maxDose is published. US cross-check (§2.2): 'Initiate treatment in adults with 50 mcg to 100 mcg'; premedication 50–100 micrograms IM 30–60 minutes before surgery; adjunct to regional anaesthesia 50–100 micrograms IM or slowly IV over one to two minutes; postoperatively (recovery room) 50–100 micrograms IM, repeatable in one to two hours.

The calculator uses the LOWER end of the SPC's initial range. SPC §4.2 paediatric table, verbatim — 'Children aged 2 to 11 years old: Spontaneous Respiration 2-11 yrs Initial 1-3 micrograms/kg, Supplemental 1-1.25 micrograms/kg; Assisted Ventilation 2-11 yrs Initial 1-3 micrograms/kg, Supplemental 1-1.25 micrograms/kg.' 'Children aged 12 to 17 years old: Follow adult dosage.' Verbatim safety statement: 'Techniques that involve analgesia in a spontaneous breathing child should only be used as part of an anaesthetic technique, or given as part of a sedation/analgesia technique with experienced personnel in an environment that can manage sudden chest wall rigidity requiring intubation, or apnoea requiring airway support.' No figure is given in this SPC for children under 2 years; the US label states 'The safety and efficacy of Fentanyl Citrate Injection in pediatric patients under two years of age has not been established.' The concentration used for the volume calculation is the fetched product strength — Fentanyl 50 microgram/ml Injection, i.e. 50 micrograms per mL. Intranasal dosing is NOT covered by this label. Verify all under-18 dosing against a children's formulary before administration.