Plasma theophylline concentrations measured by high-pressure liquid chromatography

We present a specific, sensitive high-pressure liquid-chromatographic assay for theophylline in plasma. Only 0.5 ml of plasma is required for each determination, and the lower limit of detection by this method is 0.1 mg/liter. Other xanthines and their metabolites do not interfere. This method is suitable for use in studying the pharmacokinetics of this drug in infants and children, from whom only small volumes of blood are available.