Fentanyl Citrate: Chemical Structure, Mechanism of Action, Structural Activity Relationship, Synthesis, Uses & Side Effects

Chemical Structure:

• C22H28N2O · C6H8O7

Chemical Structure

Mechanism of Action:

• ·        A potent synthetic opioid agonist, primarily at mu-receptors. It's much more potent than morphine, leading to profound analgesia.

Structural Activity Relationship (SAR) of Fentanyl:

1..Phenethylamine Core:

• Fentanyl has a phenethylamine core structure, fundamental to its opioid activity. Modifications here can alter potency and receptor affinity.

2.N-Phenyl-N-(piperidin-4-yl)propanamide Backbone:

• The piperidine ring and its substitution pattern are crucial for activity. The 4-anilidopiperidine motif is particularly important for fentanyl's potency.

3.N-Propionyl Group:

• The propionyl group at the nitrogen atom of the piperidine ring is significant for fentanyl's high affinity for the mu-opioid receptor.

4.Substitutions on the Phenyl Ring:

• Various substitutions on the phenyl ring (attached to the piperidine nitrogen) can significantly affect potency, selectivity, and pharmacokinetics.

5.Lipophilicity:

• Fentanyl's high lipophilicity, which aids in crossing the blood-brain barrier, contributes to its rapid onset of action.

SAR of Fentanyl

Synthesis of Fentanyl Citrate

The synthesis of fentanyl involves several steps. A simplified version is as follows:

Synthesis of 4-Anilinopiperidine:

• 4-Piperidinone+Aniline → 4-Anilinopiperidine

Formation of the Propanamide:

• 4-Anilinopiperidine + Propionyl chloride → Fentanyl Base

Conversion to Citrate Salt:

• Fentanyl Base + Citric Acid →Fentanyl Citrate

• Each reaction requires specific conditions (like temperature, solvent, catalysts) and must be carefully controlled to ensure the purity and efficacy of the final product. The synthesis process involves complex organic chemistry techniques, and understanding it is crucial for pharmaceutical development and modification of fentanyl analogs.

Uses:

• Severe Pain: Used in managing severe pain, including cancer pain.

• Anesthesia: As an adjunct for anesthesia due to its rapid onset and short duration of action.

• Chronic Pain: Administered via transdermal patches for long-term pain management.

Side Effects:

• Respiratory Depression: More pronounced than with many other opioids.

• CNS Effects: Including sedation, dizziness, and confusion.

• GI Disturbances: Nausea and constipation are common.