There are four principal protein targets with which drugs can interact:
* Enzymes (e.g. neostigmine and acetyl cholinesterase)
** Inhibitors
** Inducers 
** Activators 
* Membrane carriers [<nowiki/>Reuptake vs Efflux] (e.g. tricyclic antidepressants and catecholamine uptake-1)
** Enhancer (RE)
** Inhibitor (RI)
** Releaser (RA)
* Ion channels (e.g. nimodipine and voltage-gated Ca channels)
** Blocker
** Opener
* Receptor (e.g. Listed in table below)
** Agonists can be full, partial or inverse.
** Antagonists can be competitive, non-competitive, or uncompetive.
** Allosteric modulator can have 3 effects within a receptor. One is its capability or incapability to activate a receptor (2 possibilities). The other two are agonist affinity and efficacy. They may be increased, decreased or unaffected (3 and 3 possibilities).
NMBD = neuromuscular blocking drugs; NMDA = N-methyl-d-aspartate; EGF = epidermal growth factor.