The primary mechanism by which caffeine produces its stimulating effects is by blocking cell surface receptors known as adenosine receptors. In doing so, it reverses certain types of inhibitory neurotransmission. While everyone feels some degree of stimulation from caffeine, some of us feel unpleasantly anxious after caffeine ingestion. This may be due to a polymorphism in the adenosine type 2A receptor (ADORA2A) gene (rs5751876; C1083T) which renders the receptors more amenable to caffeine inhibition. Carriers may experience an unpleasant level of anxiety after ingestion of caffeine . This pharmacodynamic sensitization may be exacerbated by pharmacogenetic flaws in metabolic clearance, such as the common CYP1A2 variant (rs762551) which significantly prolongs the half-life of the drug .