Fentanyl is a potent synthetic opioid agonist that belongs to the phenylpiperidine derivative class of drugs. It is structurally related to meperidine and is known for its remarkable potency, being 75 to 125 times more potent than morphine. Fentanyl was first synthesized in 1960 by Janssen Pharmaceutica and is commonly available as its citrate salt under the trade name Sublimaze.

Potency75 to 125 times more potent than morphine
Onset and Duration of ActionRapid onset, shorter duration compared to morphine
Blood-Brain Barrier PenetrationRapid due to high lipid solubility
Tissue DistributionExtensive distribution into highly vascular tissues
MetabolismExtensively metabolized by N-demethylation
Elimination Half-TimeLonger than morphine due to larger volume of distribution
Context-Sensitive Half-TimeProlongs with prolonged infusion

Note: Fentanyl has a rapid onset of action due to its high lipid solubility, which facilitates its passage across the blood-brain barrier. It has a longer elimination half-time than morphine, primarily due to its larger volume of distribution.

Clinical Uses
Clinical ApplicationRecommended Doses and Routes
Analgesia– Low doses (1 to 2 μg/kg IV) for analgesia
Adjunct to Inhalation Anesthetics– As an adjuvant to inhaled anesthetics to blunt circulatory responses to laryngoscopy or surgical stimulation
Surgical Anesthesia– Large doses (50 to 150 μg/kg IV) for surgical anesthesia
Transmucosal Preparations– Oral transmucosal fentanyl for preoperative sedation and induction of anesthesia
Transdermal Patch– Long-term, sustained analgesia for chronic pain (e.g., cancer-related pain)

Note: Fentanyl can be administered in various ways depending on the clinical need, including intravenous, transmucosal, and transdermal routes.

Side Effects
Side EffectDescription
Respiratory DepressionCan lead to hypoventilation
Cardiovascular Effects– Bradycardia – Hypotension (minimal histamine release)
Seizure ActivityRare but reported following rapid IV administration
Somatosensory Evoked PotentialsMay produce changes but typically do not interfere with monitoring
Intracranial PressureModest increases in ICP, especially in head injury patients
Drug Interactions– Potentiates the effects of benzodiazepines – Decreases propofol dose requirements

Note: Fentanyl can cause respiratory depression, and caution is needed when combining it with other central nervous system depressants.


Leave a Comment