A method of inhibiting formation of cancerous metabolites, of inhibiting cytochrome P450 2A13 from forming carcinogen metabolites, and/or inhibiting formation of cancerous lung cells in a subject can include: providing a morpholine compound that selectively interacts with cytochrome P450 2A13 over cytochrome P450 2A6; administering a therapeutically effective amount of the morpholine compound or derivative to the subject. The morpholine compound or derivative can be substantially more selective for interacting with the cytochrome P450 2A13 over the cytochrome P450 2A6. The morpholine compound or derivative can also be substantially non-interactive with other physiological components. The morpholine compound or derivative can include a structure that selectively interacts with cytochrome P450 2A13 over cytochrome P450 2A6, such as Compounds 1-34 of Formulas A-D.