Hemodynamic and Humoral Effects of Caffeine in Autonomic Failure

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Abstract
We examined the effects of caffeine and meals on blood pressure and heart rate in 12 patients with autonomic failure. The influence of caffeine on plasma norepinephrine, epinephrine, and renin activity was also studied. Caffeine 250 mg, raised blood pressure by 12/6 mm Hg, from 129±25/78±12 (mean±S.D.) to a maximum of 141±30/84±16 mm Hg at 45 minutes (P<0.01), but did not change heart rate, levels of norepinephrine, or epinephrine, or plasma renin activity. Blood pressure fell by 28/18 mm Hg after a standardized meal, from 133±32/80±15 to a minimum of 105±21/62±12 mm Hg at 60 minutes (P<0.01 ). After pretreatment with 250 mg of caffeine, the standardized meal induced a fall of only 11/10 mm Hg, from 140±33/79±7to 129±31/69±13 mm Hg at 60 minutes (P<0.05 vs. values after the control meal). After long-term administration of caffeine (250 mg per day for seven days) in five patients, postprandial blood pressures remained higher after caffeine than after placebo (P<0.05).