Opioids
An opioid is a chemical substance that has a morphine-like action in the body. Most opioids are not legal for over the counter purchase; However, some products that are legal (poppy seeds, poppy pods, and poppy plant material) contain morphine, codeine, and other analgesic opiates. Many of these products may be purchased legally but it is illegal to use them for anything other than cooking and decorative purposes. Codeine can be purchased over the counter in some jurisdictions, but it's usually mixed with Paracetamol to discourage abuse. The paracetamol, however, can be removed fairly easily by manipulation of the different solubility of paracetamol and codeine in cold water.
Read more about this topic: Legal Intoxicant