Pharmacological properties : תכונות פרמקולוגיות

Pharmacodynamic Properties

5.1   Pharmacodynamic properties
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.

Pharmacokinetic Properties

5.2   Pharmacokinetic properties
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.
Renal impairment
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).
Obese Patients
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).