Opioids are morphine-like drugs. Morphine is a 'naturally occurring' drug. That is, it is extracted from a plant just like other 'herbal remedies'. The plant which 'grows' morphine is the opium poppy: papaver somniferum. Morphine can be found along with a variety of over 20 similar substances (like codeine) in the dried seed capsules of this plant. The mixture is called opium.

Whilst morphine and codeine are naturally drugs, other 'morphine-like' drugs like pethidine, fentanyl, sufentanyl and alfentanyl are synthetic.