What is carfentanil? Carfentanil or carfentanyl is a structural analog of the synthetic opioid analgesic fentanyl. Short-acting and with fast onset, it has weight for weight, around 100 times stronger effects than fentanyl and 1000 times stronger than heroin. Carfentanil is illegally manufactured for sale on the streets. As well as being added to substances […]