Source: Medicines & Healthcare Products Regulatory Agency (GB) Revision Year: 2021 Publisher: Piramal Critical Care Limited, Suite 4, Ground Floor, Heathrow Boulevard East Wing, 280 Bath Road, West Drayton, UB7 0DQ, United Kingdom
Pharmacotherapeutic group: Anaesthetic general, opioid anaesthetic
ATC code: N01AH01
Fentanyl is a synthetic opiate with a clinical potency of 50 to 100 times that of morphine. Its onset of action is rapid and its duration of action is short. In man, a single IV dose of 0.5-1 mg/70 kg body weight immediately produces a pronounced state of surgical analgesia, respiratory depression, bradycardia and other typical morphine-like effects. The duration of action of the peak effects is about 30 minutes. All potent morphine-like drugs produce relief from pain, ventilatory depression, emesis, constipation, physical dependence, certain vagal effects and varying degrees of sedation. Fentanyl, however, differs from morphine not only by its short duration of action but also by its lack of emetic effect and minimal hypotensive activity in animals.
Some pharmacokinetic parameters for fentanyl are as follows:
Urinary excretion = 8%
Bound in plasma = 80%
Clearance (ml/min/kg) = 13 ± 2
Volume of distribution (litres/kg) = 4.0 ± 0.4
Estimates of terminal half-life range from 141 to 853 minutes.
Data obtained from a study administering IV fentanyl in patients undergoing renal transplantation suggest that the clearance of fentanyl may be reduced in this patient population. If patients with renal impairment receive fentanyl, they should be observed carefully for signs of fentanyl toxicity and the dose reduced if necessary (see section 4.2 Posology and method of administration).
An increase in clearance of fentanyl is observed with increased body weight. In patients with a BMI >30, clearance of fentanyl increases by approximately 10% per 10 kg increase of the fat free mass (lean body mass).
In vitro fentanyl showed, like other opioid analgesics, mutagenic effects in a mammalian cell culture assay, only at cytotoxic concentrations and along with metabolic activation. Fentanyl showed no evidence of mutagenicity when tested in in vivo rodent studies and bacterial assays. In a two-year rat bioassay, fentanyl was not carcinogenic.
Some tests on female rats showed reduced fertility as well as embryo mortality. These findings were related to maternal toxicity and not a direct effect of the drug on the developing embryo. There was no evidence of teratogenic effects.
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