Slow-release drugs are specially designed preparations that ensure that the active ingredient of the drug is released in the human body in a delayed, prolonged, uniform and thus controlled manner. This reduces the risk of undesirable side effects when the drug is taken. Retarded drugs are available as tablets, capsules, transdermal patches, injection solutions and as suspensions.

Note on mixed use of sustained-release medications together with other psychoactive substances.: The active ingredient of the sustained-release medication is released over a longer period of time and can lead to interactions with other substances for a correspondingly long time.

Non-retarded drugs release the active ingredient all at once, which can lead to undesirable side effects and increase the risk of overdose.