Heroin belongs to the group of painkilling drugs known as opiates, derived from the opium poppy. In themselves, opiates are relatively safe drugs, and are used by doctors for treating severe pain, such as that in cancer patients.

However, heroin is a Class A drug. This means it's classified by the government as one of the most dangerous and harmful drugs, alongside cocaine and crack, and getting caught with it can mean seven years in prison.