A composition suitable for use in a nicotine replacement therapy product comprising synthetic nicotine substantially free of one or more contaminants and / or impurities normally associated with tobacco-derived nicotine. For example, the synthetic nicotine is substantially free of nicotine-1'-N-oxide, nicotine diene, nicotine nordiene, 2',3-bipyridine, cotinine, anabacin and / or Or one or more of anatapin. The composition further comprises one or more pharmaceutically acceptable excipients, additives and / or carriers. Nicotine replacement therapy products may comprise any number of such products, including transdermal nicotine delivery patches, nicotine gum, synthetic chewing tobacco, synthetic snus, and synthetic tobacco rods (eg, dissolvable synthetic tobacco). Additionally, methods of treating nicotine addiction include administering a nicotine replacement composition, eg, via a nicotine replacement therapy product, to a user.