NicVAX is administered by injection into the arm; the 3'-aminomethylnicotine molecule found in the vaccine instigates an immune response in which 'nicotine' antibodies are created. The antibodies bind to nicotine molecules, causing the nicotine-antibody complexes to be too large to enter the brain; this prevents nicotine from being able to affect addiction-relevant pathways in the brain. The idea behind the drug is that since often even a single cigarette can deliver enough nicotine to the brain to reinstate the addiction, blocking the entry of nicotine into the brain might prevent this renewed dependence. This treatment works for nicotine addiction from any source. "Clinical Pharmacology & Therapeutics" considers this method "attractive," since the antibody does not enter the brain; as a result, side effects on the central nervous system are minimal, if any. Additionally, the antibodies produced bind only to nicotine and not to nicotine metabolites or any similar endogenous structures such as acetylcholine.