Prodrugs are substances which are pharmacologically inactive when taken or which are less active precursors of a drug. They develop into the actual active form through a conversion step (metabolic process or metabolization) in the body.

Prodrugs are used in medical applications in which the active ingredient would not reach the desired site of action directly, or would reach it only slightly or not selectively enough. In addition, side effects can be reduced, for example.

Prodrugs support or improve the (medical) application of an established drug.

The term prodrug is also used for recreational drug use. These are often offered on the Internet as legal alternatives to known, illegalized substances. These can be, for example, variations of the illegal LSD-25. These products(1V-LSD or 1P-LSD) are then available in Clearweb stores until the substance is banned via the Narcotics Act. These substances are converted into active LSD-25 in the body through a metabolic process. However, there is often no sound information on side effects and risks, and the effect may be different from LSD-25.