Methylxanthines reduce in vitro human overall platelet metabolism as measured by microcalorimetry.

The effect in vitro of caffeine, theophylline and enprofylline on overall platelet metabolism was investigated by a sensitive microcalorimetric method. Platelet heat production rate was found to be decreased significantly in the presence of any of the three methylxanthines in mM concentrations. Also lower caffeine concentration, as occurring during normal coffee intake, reduced platelet metabolism. These results show that, firstly, methylxanthines have a direct influence on platelet metabolism, and secondly, microcalorimetry can be used as a new and sensitive tool for investigating the influence of drugs on blood cell metabolism.