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alfentanil injection, USP Dosage and Administration

2 DOSAGE AND ADMINISTRATION

2.1 Important Dosage and Administration Instructions

Alfentanil injection should be administered only by persons specifically trained in the use of intravenous anesthetics and management of the respiratory effects of potent opioids.

In patients administered high doses of alfentanil injection, it is essential that qualified personnel and adequate facilities are available for the management of postoperative respiratory depression.

  • Ensure that an opioid antagonist, resuscitative and intubation equipment, and oxygen are readily available.
  • Individualize dosage based on factors such as age, body weight, physical status, underlying pathological condition, use of other drugs, type of anesthesia to be used, and the surgical procedure involved.
  • The selection of preanesthetic medications should be based upon the needs of the individual patient.
  • The neuromuscular blocking agent selected should be compatible with the patient's condition, taking into account the hemodynamic effects of a particular muscle relaxant and the degree of skeletal muscle relaxation required.
  • Patients receiving monitored anesthesia care (MAC) should be continuously monitored by persons not involved in the conduct of the surgical or diagnostic procedure; oxygen supplementation should be immediately available and provided where clinically indicated; oxygen saturation should be continuously monitored; the patient should be observed for early signs of hypotension, apnea, upper airway obstruction and/or oxygen desaturation.
  • Delayed respiratory depression, respiratory arrest, bradycardia, asystole, arrhythmias and hypotension have also been reported. Therefore, vital signs must be monitored continuously, including following the termination of surgery.
  • Inspect parenteral drug products visually for particulate matter and discoloration prior to administration, whenever solution and container permit.
  • For purposes of administering small volumes of alfentanil injection accurately, the use of a tuberculin syringe or equivalent is recommended.

As with other potent opioids, the respiratory depressant effect of alfentanil may persist longer than the measured analgesic effect. The total dose of all opioid agonists administered should be considered by the practitioner before ordering opioid analgesics during recovery from anesthesia.

If alfentanil injection is administered with a CNS depressant, become familiar with the properties of each drug, particularly each product's duration of action. In addition, when such a combination is used, fluids and other countermeasures to manage hypotension should be available [see Warnings and Precautions (5.5)].

The physical and chemical compatibility of alfentanil injection have been demonstrated in solution with normal saline, 5% dextrose in normal saline, 5% dextrose in water and Lactated Ringers. Clinical studies of alfentanil injection infusion have been conducted with alfentanil injection diluted to a concentration range of 25 mcg/mL to 80 mcg/mL.

As an example of the preparation of alfentanil injection for infusion, 20 mL of alfentanil injection added to 230 mL of diluent provides 40 mcg/mL solution of alfentanil.

2.2 Dosage

The dosage of alfentanil injection should be individualized and titrated to the desired effect in each patient according to body weight, physical status, underlying pathological condition, use of other drugs, and type and duration of surgical procedure and anesthesia. The dose of alfentanil injection should be reduced in elderly or debilitated patients [see Warnings and Precautions (5.6)].

See Dosing Chart for the use of alfentanil injection

1)
by incremental injection as an analgesic adjunct to anesthesia with barbiturate/nitrous oxide/oxygen for short surgical procedures (expected duration of less than one hour);
2)
by continuous infusion as a maintenance analgesic with nitrous oxide/oxygen for general surgical procedures; and
3)
by intravenous injection in anesthetic doses for the induction of anesthesia for general surgical procedures with a minimum expected duration of 45 minutes; and
4)
by intravenous injection as the analgesic component for monitored anesthesia care (MAC).

When administering alfentanil as induction doses, administer the dose slowly (over three minutes). Because administration of the induction dose may produce loss of vascular tone and hypotension, consider given to fluid replacement prior to induction.

Table 1: Dosing Chart For Use During General Anesthesia
Spontaneously Breathing/Assisted VentilationInduction of Analgesia: 8 to 20 mcg/kg
Maintenance of Analgesia: 3 to 5 mcg/kg q 5 to 20 min or 0.5 to 1 mcg/kg/min
Total dose: 8 to 40 mcg/kg
 
Assisted or Controlled Ventilation
- Assisted or Controlled Ventilation
Incremental Injection

(To attenuate response to laryngoscopy and intubation)
Induction of Analgesia: 20 to 50 mcg/kg
Maintenance of Analgesia: 5 to 15 mcg/kg q 5 to 20 min
Total dose: Up to 75 mcg/kg
 
Assisted or Controlled Ventilation
- Continuous Infusion

(To provide attenuation of response to intubation and incision)
Induction of Analgesia: 50 to 75 mcg/kg
Maintenance of Analgesia: 0.5 to 3 mcg/kg/min (Average rate 1 to 1.5 mcg/kg/min)
Infusion rates are variable and should be titrated to the desired clinical effect. See Infusion Dosage Guidelines Below
Total dose: Dependent on duration of procedure
 
Anesthetic InductionInduction of Anesthesia: 130 to 245 mcg/kg
Administer slowly (over 3 minutes).
Maintenance of Anesthesia: 0.5 to 1.5 mcg/kg/min or general anesthetic.
Infusion rates are variable and should be titrated to the desired clinical effect. See Infusion Dosage Guidelines Below
Total dose: Dependent on duration of procedure
At these doses truncal rigidity should be expected and a muscle relaxant should be utilized.
In patients administered anesthetic (induction) dosages of alfentanil injection, it is essential that qualified personnel and adequate facilities are available for the management of intraoperative and postoperative respiratory depression.
 
MONITORED ANESTHESIA CARE (MAC)
(For sedated and responsive, spontaneously breathing patients)
Induction of MAC: 3 to 8 mcg/kg
Maintenance of MAC: 3 to 5 mcg/kg q 5 to 20 min or 0.25 to 1 mcg/ kg/min
Infusion rates are variable and should be titrated to the desired clinical effect. See Infusion Dosage Guidelines Below
Total dose: 3 to 40 mcg/kg
Patients receiving monitored anesthesia care (MAC) should be continuously monitored by persons not involved in the conduct of the surgical or diagnostic procedure
 

Infusion Dosage Guidelines For Continuous Infusion: 0.5 to 3 mcg/kg/min administered with nitrous oxide/oxygen in patients undergoing general surgery.
Following an anesthetic induction dose of alfentanil injection, alfentanil infusion rate requirements are reduced by 30% to 50% for the first hour of maintenance. Requirements for volatile inhalation anesthetics are also reduced by 30% to 50% for the first hour of maintenance.
Changes in vital signs that indicate a response to surgical stress or lightening of anesthesia may be controlled by increasing the alfentanil injection to a maximum of 4 mcg/kg/min and/or administration of bolus doses of 7 mcg/kg. If changes are not controlled after three bolus doses given over a five-minute period, a barbiturate, vasodilator, and/or inhalation agent should be used. Infusion rates should always be adjusted downward in the absence of these signs until there is some response to surgical stimulation.
Rather than an increase in infusion rate, 7 mcg/kg bolus doses of alfentanil injection or a potent inhalation agent should be administered in response to signs of lightening of anesthesia within the last 15 minutes of surgery. Alfentanil injection infusion should be discontinued at least 10 to 15 minutes prior to the end of surgery.
In patients administered anesthetic (induction) dosages of alfentanil injection, it is essential that qualified personnel and adequate facilities are available for the management of intraoperative and postoperative respiratory depression.

2.3 Discontinuation of Alfentanil Injection

Alfentanil injection infusions should be discontinued at least 10 to 15 minutes prior to the end of surgery during general anesthesia. During administration of alfentanil injection for Monitored Anesthesia Care (MAC), infusions may be continued to the end of the procedure.

2.4 Dosage Modification in Elderly Patients

Reduce the initial dose of alfentanil injection in elderly patients by up to 40% due to reduced clearance and increased sensitivity to the effects [see Specific Populations (8.5)]. The effect of the initial dose should be considered in determining supplemental doses.

2.5 Dosage Modifications in Obese Patients

In obese patients (more than 20% above ideal body weight) the dose of alfentanil injection should be determined on the basis of lean body weight.

2.6 Dosage Modifications with Concomitant Use with Other CNS Depressants

Other CNS depressant drugs (e.g. barbiturates, tranquilizers, narcotics and general anesthetics) will have additive or potentiating effects with alfentanil injection. When patients have received such drugs, the dose of alfentanil injection, required will be less than usual. Following the administration of alfentanil injection, the dose of other CNS depressant drugs should be reduced [see Drug Interactions (7)].

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