Persistent cardiovascular effects with repeated caffeine administration.

Although habitual caffeine users ingest the drug repeatedly throughout each day, the persistence of caffeine's known cardiovascular effects with such repeated use has not been investigated. Blood pressure and heart rate were measured under resting conditions in 10 healthy, male coffee or tea drinkers for 2 hours following a pretreatment dose of caffeine (125 mg) on two separate days after overnight abstinence. Either a second caffeine dose or placebo was administered and measurements continued for 1.5 hours. Compared to placebo, the second dose of caffeine produced significant increases in heart rate and diastolic and mean arterial, but not systolic, blood pressures. The results suggest that the cardiovascular effects of caffeine may persist throughout the day with repeated administration of moderate amounts of caffeine. Habitual caffeine use does not necessarily lead to complete tolerance, which suggests that caffeine's cardiovascular effects could contribute to an increased risk of cardiovascular disease.