Alfentanil

Alfentanil: Uses, Dosage and Side Effects

Overview

• Very potent opioid analgesic.
• Action: Pure mu agonist of the phenylpiperidine series.

Uses of Alfentanil

• Used to make intraoperative analgesia during anaesthesia in dogs and cats, this opioid analgesic is extremely strong (10–20 times more potent than morphine).
• Contributes to a balanced anaesthesia technique but they must be administered accurately. It has a rapid onset (15–30 seconds) and short duration of action. It is best given using continuous rate infusions.

Dose of Alfentanil in Dogs and Cats

Dogs:

0.001–0.005 mg/kg i.v. as a single bolus or 0.001–0.0025 mg/kg/min continuous rate infusion.

Cats:

0.001 mg/kg i.v. as a single bolus or 0.001 mg/kg/min continuous rate infusion.

Side Effects of Alfentanil in Dogs and Cats

• Bradycardia.
• Respiratory depression.
• Do not use unless facilities for positive pressure ventilation are available (either manual or automatic).
• Rapid i.v. injection can cause severe bradycardia, even asystole.

Contraindications of Alfentanil in Dogs and Catse.

No data are available.

Some Notes:

• Alfentanil at least 50% lowers the dose required for anesthetics that are delivered simultaneously, including anesthetics for inhalation.
• It is recommended to avoid administering alfentanil to patients taking monoamine oxidase inhibitors
• It is recommended to avoid administering alfentanil with these drugs due to occurrence of interactions between each other:
  • Acepromazine, amitriptyline, atropine, clomipramine, glycopyrrolate: Increase risk for urinary retention, constipation, and CNS and respiratory depression
  • Bethanechol: antagonize the beneficial effects of bethanechol on GI motility
  • amiodarone, anesthetic agents, beta-adrenergic antagonists (atenolol, propranolol), digoxin: produce bradycardia or hypotension
  • anesthetic agents, barbiturates ( phenobarbital), benzodiazepines (diazepam, midazolam), cannabidiol: increase the risk for CNS and/or respiratory depression
  • Desmopressin: increase concentrations of desmopressin and increase the risk for water intoxication and/or hyponatremia, which can progress to seizures, coma, respiratory arrest, and death. Monitor electrolytes and renal function.
  • Furosemide: Opioids may decrease the therapeutic effects of diuretics
  • Drugs that induce hepatic isoenzymes (griseofulvin, mitotane, phenobarbital): decrease the concentration of alfentanil. Monitor clinical response
  • Drugs that inhibit hepatic isoenzymes (cimetidine, diltiazem, erythromycin, fluconazole, itraconazole, ketoconazole): increase the half-life and decrease the clearance of alfentanil leading to prolonged effects and an increased risk for respiratory depression
  • Hypotensive Agents(eg, amlodipine, enalapril, telmisartan): increases risk for bradycardia, hypotension, and orthostasis. Use combination with caution; monitor blood pressure and heart rate.
  • Ifosfamide: Concurrent use may increase risk for neurotoxicity including somnolence, confusion, hallucinations, blurred vision, urinary incontinence, seizures, and coma. Use cautiously and monitor.
  • Iohexol: Concurrent use of opioids with intrathecal iohexol may increase risk for seizures. Opioids should be withheld for 48 hours before and 24 hours after intrathecal administration of iohexol.
  • Loperamide: Concurrent use may increase risk for constipation.
  • Monoamine oxidase inhibitors ( Amitraz, Selegiline): may increase risk for anxiety, confusion, hypotension, respiratory depression, cyanosis, and coma. MAOIs should be withheld for 14 days prior to administration of opioids. Avoid combination.
  • Neuromuscular blocking agents (atracurium, pancuronium): may increase risk for tachycardia, bradycardia, and/or hypotension. Use combination with caution; monitor heart rate and blood pressure.
  • Prokinetic agents (cisapride, erythromycin, metoclopramide): may antagonize the prokinetic effects.