Caffeine is a methylxanthine derivative
that is contained in tea, coffee, chocolate,
and beverages and in compound analgesic
preparations. Caffeine is a proven ergogenic
aid, increasing athletic performance,
endurance, and mental chronometry even at
very low doses.13 As a consequence of this
it is likely that caffeine-containing products
will reduce the efficacy of hypnotics and
increase the risk of insomnia. Patients on
antiarrythmics should also avoid excessive
caffeine because of the risk of tachycardias.