A classification of drug substances according to their mechanism of action.

Different classification systems for therapeutic agents exist. The most commonly used one is the ATC Code (ATC: Anatomy, Therapeutic properties, Chemical, pharmacological properties). Here, an alternative classification system (TCAT: Target-Chemistry-Anatomy-Therapy) is proposed which refers to the molecular mechanism of action or rather, target. The main subgroups of targets are: enzymes; substrates, metabolies, proteins; receptors; ion channels; transporter molecules and systems; nucleic acids, ribosomes; physicochemical mechanisms; antigen-antibody reactions; unknown targets. This target-oriented approach may be particularly useful in teaching advanced medicinal chemistry.