Adrenergic modifiers bind to epinephrine receptors while cholinergic modifiers bind to ACh receptors. Either of these drugs will inhibit the natural ligand actions or mimic the natural ligand molecules when it binds to the receptor.
Epinepherine can be classified as adrenergic, even though it is a natural ligand (chemical). Pilocarpine is a good example of a cholinergic chemical.