Heroin is a depressant drug, which means it slows down the messages travelling between your brain and body. Heroin belongs to a group of drugs known as ‘opioids’ that are from the opium poppy. 1. Heroin comes in different forms including:1  Fine white powder. 2  Coarse off-white granules.eroin belongs to a group of drugs known as ‘opioids’ that are from the opium poppy. 1. Heroin comes in different forms including: 1  Fine white powder. 2  Coarse off-white granules.