4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone or nicotine-derived nitrosamine ketone (NNK) is a tobacco-specific nitrosamine. NNK is considered to be a carcinogen. NNK induces deleterious mutations in oncogenes and tumor suppression genes by forming DNA adducts, which could be considered as tumor initiation. Meanwhile, the binding of NNK to the nicotinic acetylcholine receptor promotes tumor growth by enhancing and deregulating cell proliferation, survival, migration, and invasion, thereby creating a microenvironment for tumor growth.

Cotinine is a product formed after the chemical nicotine enters the body. Measuring cotinine in people’s blood is the most reliable way to determine exposure to nicotine for both smokers and nonsmokers exposed to environmental tobacco smoke. Cotinine is safe, non-addictive and has pharmacokinetic properties adequate for therapeutic use. Research has shown that cotinine has antipsychotic, anxiolytic, and antidepressant properties and modulates the serotonergic, cholinergic and dopaminergic systems. Cotinine behaves as a positive allosteric modulator of the nicotinic acetylcholine receptors and has anti-inflammatory effects. Cotinine is under investigation as an agent for the treatment of depression, PTSD, schizophrenia, Alzheimer's disease and Parkinson's disease.

Nicotine is a natural alkaloid obtained from the dried leaves and stems of the nightshade family of pants, such as Nicotiana tabacum and Nicotiana rustica, where it occurs in concentrations of 0.5-8%. Cigarette tobacco varies in its nicotine content, but common blends contain 15-25 mg per cigarette, with a current trend towards lower levels. Nicotine is highly addictive substance, it exhibits a stimulant effect when adsorbed at 2 mg. Administration of higher doses could be harmful. Action of nicotine is mediated by nicotinic cholinergic receptors. Nicotine binds to the interface between two subunits of the receptors, opens the channel and allows the entry of sodium or calcium. The principal mediator of nicotine dependence is α4β2 nicotine receptor.