Metabolic effects of methylxanthines.

As predicted, methylxanthines influence several metabolic processes and increase the serum concentrations of glucose, FFAs, and catecholamines in adults. Although these increases are significant statistically, they may not be clinically important. Based upon a small number of studies, methylxanthines seem to affect infants in a more complex fashion. In infants, methylxanthines increase metabolic rate, do not increase catecholamine release, and produce variable effects on carbohydrate balance. The serum glucose concentration after methylxanthines likely represents a complex interplay of glycogen stores, types of nutrient administered, rate of nutrient administration, and degree of increased metabolic rate. Carefully controlled prospective studies are needed to determine the possible effects of methylxanthines on growth, carbohydrate balance, FFA release, and salt and water excretion at high and low serum concentrations. In addition, it is necessary to assess the effect on these variables of chronic pre- and postnatal exposure to methylxanthines.