Fentanyl

Fentanyl is indicated for the management of breakthrough pain in patients with cancer who are already receiving and who are tolerant to opioid therapy for their underlying persistent cancer pain. Patients considered opioid tolerant are those who are taking at least 60 mg of oral morphine/day, at least 25 mcg of transdermal Fentanyl/hour, at least 30 mg of oxycodone daily, at least 8 mg of oral hydromorphone daily or an equianalgesic dose of another opioid for a week or longer.

Dosage: 

• Fentanyl injection can be administered intravenously either as a bolus or by infusion & by intramuscular route also. The dose of fentanyl should be individualized according to age, body weight, physical status, underlying pathological condition, use of other drugs and type of surgery and anesthesia.

• Doses in excess of 200mcg are for use in anesthesia only. As a premedicant, 1-2 ml fentanyl may be given intramuscularly 45 minutes before induction of anesthesia. After IV administration in unpremedicated adult patients, 2ml fentanyl may be expected to provide sufficient analgesia for 10-20 minutes in surgical procedures involving low pain intensity. 10 ml fentanyl injected as a bolus gives analgesia lasting about one hour. The analgesia produced is sufficient for surgery involving moderately painful procedures. Giving a dose of 50mcglkg fentanyl will provide intense analgesia for some four to six hours, for intensely stimulating surgery.

• Fentanyl may also be given as an infusion. In ventilated patients, a loading dose of fentanyl may be given as a fast infusion of approximately 1 mcg/kg/min for the first 10 minutes followed by an infusion of approximately 0.1 mcg/kg/min. Alternatively the loading dose of fentanyl may be given as a bolus. Infusion rates should be titrated to individual patient response; lower infusion rates may be adequate. 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 mcg/kg/min. are necessary if spontaneous ventilation .is to be maintained. Higher infusion rates (up to 3 mcg/kg/min) have been used in cardiac surgery. Fentanyl is chemically incompatible with the induction agents thiopentone & methohexitone because of wide differences in pH

• Use in elderly and debilitated patients: It is wise to reduce the dosage in the elderly and debilitated patients. The effect of the initial dose should be taken into account in determining supplemental doses.

Side effects: As with other narcotic analgesics, the most common serious adverse reactions reported to occur with Fentanyl are respiratory depression, apnoea, muscular rigidity, myoclonic movements, and bradycardia. Respiratory depression is more likely to occur with intravenous administration if a dose is given too rapidly and it rarely occurs with intramuscular administration.