Of concern to you in particular may be the part about diarrhoea...Those who take these preparations without reducing their regular caffeine intake from other sources may risk developing what has been termed "caffeinism" which is caused by toxic levels of caffeine. The symptoms include nausea, diarrhoea, indigestion, irregular heartbeat and respiration, light-headedness, jitteriness and frequent urination.1 These symptoms may also develop in those not habitually exposed to caffeine who ingest a moderate dose.