Caffeine

Caffeine is a popular central nervous system (CNS) stimulant. It is a well-studied substrate of Cytochrome P450 enzymes like CYP1A2. Caffeine is taken up by transporters at the blood brain barrier. Its stimulating effects are believed to act through adenosine receptors and monoamine neurotransmitters. It is an adenosine receptor antagonist and adenosine 3',5'-cyclic monophosphate (cAMP) phosphodiesterase inhibitor. It can affect cellular calcium levels, releasing calcium from cellular stores. It has been shown to inhibit cellular DNA repair mechanisms.