While the caffeine induced cerebral vasoconstriction is well documented, the effects of oral ingestion of the drug in a dose range comparable to the quantities in which it is usually consumed and the intensity and duration of the associated reduction in cerebral circulation are unknown. Cerebral blood flow was measured via the 133Xenon inhalation technique before and thirty and ninety minutes after the oral administration of 250 mg of caffeine or a placebo, under double-blind conditions. Caffeine ingestion was found to be associated with significant reductions in cerebral perfusion thirty and ninety minutes later. The placebo group showed no differences between the three sets of cerebral blood flow values.

SEVERAL INVESTIGATORS have reported an association between alcohol abuse and cerebrovascular disease.1 "* Neuropsychiatric complications of chronic, excessive consumption of ethyl alcohol are often associated with significant reductions in cerebral blood flow (CBF).9 -" Reduction in cerebral blood flow is seen following acute ethanol withdrawal with normalization in a few days. 12Studies on the acute effect of ethanol on CBF have produced conflicting results. Most animal studies indicate a vasoconstrictive effect. -16 Sutherland and associates' 7 measured CBF and cerebral metabolism via the nitrous oxide technique, before and twenty minutes after the oral administration of 1 g of alcohol per kg body weight in eleven males with a history of problem drinking. Alcohol ingestion was not associated with any changes in CBF or the metabolic rates of oxygen consumption or carbon dioxide production. Hine and associates 18 studied ten males who had been drinking periodically or chronically for 10-25 years. CBF was measured with the nitrous oxide technique before and twenty minutes after the oral administration of .5 ml of 90 proof whiskey per kg body weight. Post ethanol CBF values showed statistically significant decrease. However, the authors stated that the CBF decrease was very modest and inconsistent in spite of the statistical significance. There were no changes in cerebral metabolic rates for oxygen. Battey and associates 19 examined the effect of intravenous infusions of 5-10 percent solutions of ethyl alcohol (average quantity -22 cc) in 15 patients convalescing from a variety of medical illnesses. CBF measurements were performed with the nitrous oxide inhalation technique before and during the infusions. CBF was also measured in a second group of subjects who were brought to the hospital emergency room with severe alcoholic intoxication, 1-2 hours after admission and 15-62 hours later, when they were sober. Low concentrations of blood alcohol (.068 mg/percent) did not produce significant changes in either cerebral blood flow or oxygen consumption. However, during severe alcohol intoxication with high