Caffeine acts as a psychoactive stimulant (CNS); it crosses the blood brain barrier where it acts as an antagonist inhibitor of adenosine. Caffeine increases epinephrine. Body size, amount of caffeine, and tolerance will vary its effect. Tea, pop and chocolate are also sources of caffeine. Considering the variability between the amount of caffeine that can be digested, the person’s body type, tolerance level and the additional drug(s) would all have to be considered before arriving at a conclusion that there is a decrease in effectiveness when pairing one drug with another. Water in excess can lead to the dilution of sodium in the body. However, I am not aware of a normal amount of water consumption interfering with the mechanism or therapeutic level of a drug(s). Specifically, what drugs are decreased in effectiveness when interacting with caffeine, tea and/or water?
