3, 4-dihydroxyphenylacetic acid (DOPAC) is a neuronal metabolite of dopamine (DA). DA undergoes monoamine oxidase-catalyzed oxidative deamination to 3,4-dihydroxyphenylacetaldehyde (DOPAL), which is metabolized primarily to 3,4-dihydroxyphenylacetic acid (DOPAC) via aldehyde dehydrogenase, ALDH2. DOPAC exhibits the antiproliferative effect in colon cancer cells. In addition, DOPAC enhances not only the total ALDH activity but also the gene expression of ALDH1A1, ALDH2, and ALDH3A1 in a concentration-dependent manner. The pretreatment of DOPAC completely protects the cells from the acetaldehyde-induced cytotoxicity, thus DOPAC acts as a potential ALDH inducer to prevent the alcohol-induced abnormal reaction.

N-isopropyl-N'-phenylparaphenylenediamine (IPPD), an amine antiozonant, is used in rubber manufacture and is a human allergen.

Tacrine is a parasympathomimetic- a reversible cholinesterase inhibitor that is indicated for the treatment of mild to moderate dementia of the Alzheimer's type. An early pathophysiological feature of Alzheimer's disease that is associated with memory loss and cognitive deficits is a deficiency of acetylcholine as a result of selective loss of cholinergic neurons in the cerebral cortex, nucleus basalis, and hippocampus. Tacrine is postulated to exert its therapeutic effect by enhancing cholinergic function. This is accomplished by increasing the concentration of acetylcholine at cholinergic synapses through reversible inhibition of its hydrolysis by acetylcholinesterase. If this proposed mechanism of action is correct, tacrine's effect may lessen as the disease progresses and fewer cholinergic neurons remain functionally intact. There is no evidence that tacrine alters the course of the underlying dementing process. The mechanism of tacrine is not fully known, but it is suggested that the drug is an anticholinesterase agent which reversibly binds with and inactivates cholinesterases. This inhibits the hydrolysis of acetylcholine released from functioning cholinergic neurons, thus leading to an accumulation of acetylcholine at cholinergic synapses. The result is a prolonged effect of acetylcholine. is used for the palliative treatment of mild to moderate dementia of the Alzheimer's type. Tacrine was marketed under the trade name Cognex. Because of its liver toxicity and attendant requirement for monitoring liver function, tacrine prescriptions dropped after other acetylcholinesterase inhibitors were introduced, and its use has been largely discontinued.

Levamisole (the trade name Ergamisol), an anthelminthic drug with immunological properties. It also has antitumor activity when administered with 5-fluorouracil in patients with Duke's C colorectal carcinoma; however, this use was discontinued. The mechanism of the antitumor effect is unknown but has been postulated to be related to levamisole's immunomodulatory properties. Levamisole can stimulate antibody formation to various antigens, enhance T-cell responses by stimulating T-cell activation and proliferation, potentiate monocyte and macrophage functions including phagocytosis, chemotaxis and increases motility, adherence, and chemotaxis. Levamisole inhibits alkaline phosphatase and possesses cholinergic activity. The mechanism of action of levamisole as an antiparasitic agent, for example, to treat ascariasis, relates to its agonistic activity to L-subtype nicotinic acetylcholine receptors in nematode muscles. In addition, levamisole was studied for preventing relapses of the steroid-sensitive idiopathic nephrotic syndrome (SSINS). It was shown, that alone or in combination with steroids, the drug can prolong the time to relapse and prevented recurrence during one year of treatment. However, these studies also were also discontinued.