Phenylacetic acid (abr. PAA and synonyms are: α-toluic acid, benzeneacetic acid, alpha tolylic acid, 2-phenylacetic acid, β-phenylacetic acid) is an organic compound containing a phenyl functional group and acarboxylic acid functional group. Because it is used in the illicit production of phenylacetone (used in the manufacture of substituted amphetamines), it is subject to controls in countries including the United States and China Phenylacetic acid is used in some perfumes, possessing a honey-like odor in low concentrations, and is also used in penicillin G production. It is also employed to treat type II hyperammonemia to help reduce the amounts of ammonia in a patient's bloodstream by forming phenylacetyl-CoA, which then reacts with nitrogen-rich glutamine to form phenylacetylglutamine. This compound is then secreted by the patient's body. In Phase 2 of clinical research it investigated in the treatment of Brain and Central Nervous System Tumors.

Tropicamide (Mydriacyl) is an anticholinergic used as a mydriatic.Tropicamide belongs to the group of medicines called anti-muscarinics. Tropicamide blocks the receptors in the muscles of the eye (muscarinic receptors). These receptors are involved controlling the pupil size and the shape of the lens. By blocking these receptors, tropicamide produces dilatation of the pupil (mydriasis) and prevents the eye from accommodating for near vision (cycloplegia). Tropicamide is given as eye drops to dilate the pupil and relax the lens so that eye examinations can be carried out thoroughly.

Tropic acid (Tropate) is a chiral substance, existing as either a racemic mixture or as a single enantiomer. Tropate is classified as a beta hydroxy acid or a Beta hydroxy acid derivative. Beta hydroxy acids are compounds containing a carboxylic acid substituted with a hydroxyl group on the C3 carbon atom. Tropate is considered to be soluble (in water) and acidic. Tropate can be synthesized from hydratropic acid and propionic acid. Tropate can be synthesized into tropan-3alpha-yl 3-hydroxy-2-phenylpropanoate. Tropic acid is proposed be used topicaly for the treatment of wrinkles.