Fentanyl is a potent opioid analgesic, intended for buccal mucosal administration. It is designed to be placed and retained within the buccal cavity for a period sufficient to allow disintegration of the tablet and absorption of Fentanyl across the oral mucosa. Following buccal administration Fentanyl is readily absorbed with a bioavailability of 65%. The plasma protein binding of Fentanyl is 80-85%. Fentanyl is metabolized in the liver and in the intestinal mucosa to nor-fentanyl by cytochrome P450. Fentanyl is primarily (>90%) eliminated by biotransformation. The metabolites are mainly excreted in the urine, while fecal excretion is less important.
Opifen Injection 50 mcg/ml
Starting Dose: The initial dose of Fentanyl should be 100 mcg.
Re-dosing patients within a single episode: Dosing may be repeated once during a single episode of breakthrough pain if pain is not adequately relieved by one Fentanyl dose. Re-dosing may occur 30 minutes after the start of administration of Fentanyl and the same dosage strength should be used.
Increasing the dose: Titration should be initiated using multiples of the 100 mcg Fentanyl tablet. Patients require to titrate above 100 mcg can be instructed to use two 100 mcg tablets (one on each side of the mouth in the buccal cavity). If this dose is not successful in controlling the breakthrough pain episode, the patient may be instructed to place two 100 mcg tablets on each side of the mouth in the buccal cavity (total of four 100 mcg tablets). Titrate above 400 mcg by 200 mcg increments bearing in mind using more than 4 tablets simultaneously has not been studied and it is important to minimize the number of strengths available to patients at any time to prevent confusion and possible overdose. To reduce the risk of overdose during titration, patients should have only one strength of Fentanyl tablet available at any one time.
Dosage Adjustment: Generally, the dose of Fentanyl should be increased when patients require more than one dose per breakthrough pain episode for several consecutive episodes.
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.
Intractable chronic pain:
Adult: Patches deliver fentanyl in doses that range from: 12-100 mcg/hr. Doses should be individually titrated based on previous use of opioids. Opioid-naive patients: Initially, ≤25 mcg/hr; it is recommended to initially titrate w/ low doses of short-acting opioids before starting fentanyl patches. Patients receiving a strong opioid analgesic: Initial dose should be based on the previous 24-hr opioid requirements. During transfer to fentanyl patches, previous opioid treatment should be phased out gradually. If patient requires doses >100 mcg/hr, >1 patch may be used; consider alternative or additional therapy if doses >300 mcg/hr are required. Replace patch every 72 hr and apply the new patch to a different site; avoid using the same area of skin for a few days.
Elderly: Dose reduction may be needed.