“…Consequently, the biological activities and effects of these types of species on human health are obviously resulted of their nature and structural, electronic and topological properties. Hence, the interest to study another antihistaminic agent, in this case promethazine (PTZ) [10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33], which has two N–CH 3 groups (as diphenhydramine) linked to a chiral carbon and, as a consequence two enantiomeric S and R structures are expected for their three free base, cationic and hydrochloride species. PTZ hydrochloride is a drug used to treatment of nausea, vomiting, and dizziness associated with motion sickness and, besides possesses anti-pruritic, anti-allergic, anticholinergic, antihistaminic, central nervous system depressant, and with general anaesthetics effects.…”