A chemical precursor and minor active metabolite of fentanyl. It serves as an intermediate in the synthesis of fentanyl and related analogs. While it has some opioid receptor affinity, it is far weaker than fentanyl itself and not used clinically.

Relative Potency

Potency: 

Despropionyl fentanyl is significantly less potent than fentanyl (hundreds of times weaker). Its pharmacological activity is minimal compared to fentanyl but may still contribute weakly to opioid effects if present in large amounts.

Why It Is Added

Purpose

Despropionyl fentanyl may be present as a contaminant in street fentanyl or related analogs due to incomplete synthesis.