Acute effects of ethanol, caffeine, or both on platelet aggregation, thromboxane formation, and plasma-free fatty acids in normal subjects.

The acute effects of ethanol (0.5 ml/kg b.w.) and caffeine (200 mg), alone or in combination, on platelet function and plasma lipid-lipoprotein levels, were tested in four healthy volunteers according to a Latin Square design. The effects of ethanol alone on platelet function (adrenaline- and collagen-induced aggregation, thromboxane B2 formation induced by arachidonic acid) were negligible. Conversely, caffeine significantly reduced maximal aggregation of platelets following adrenaline and collagen, 3 hours after administration; it also significantly increased thromboxane B2 formation 1 hour from administration. The intakes of caffeine and, to some extent, of ethanol at doses in the common daily range, although not profoundly affecting platelet function or lipid parameters, should be given consideration when treatments with platelet-active drugs are prescribed.