Name of the first molecule: N-diethylaminoethyl-N-benzylalanine.
1945: Diphenhydramine became available followed by Chlorpheni-ramine, Brompheniramine & Promethazine.
1976: Chlorpheniramine and Brompheni-ramine became the OTC drug. In 1980's 2nd generation Antihistamine (Cetirizine, Loratadine) & 3rd generation Antihistamine (Fexofenadine, Ebastine) became available.