While both of them belong to the same class of drug family, they differ in their manufacture and how they affect the body. Heroin, which is a semi-synthetic drug, is created from the opium poppy plant, while Fentanyl is a fully synthetic drug designed in a lab. The major difference between fentanyl and heroin is their strength. It is observed that Fentanyl is 50 times more powerful than Heroin and 100 times stronger than morphine. This major gap of potential defines that Fentanyl is much more unpredictable and can cause fatal reactions even if a small amount is consumed. Due to its concentration, the chance of overdose reaction becomes faster than Heroin. It can cause breathing problems even in small amount consumption, which later can be converted into a high emergency condition.