Simultaneous high-performance liquid chromatographic determination of caffeine and theophylline for routine drug monitoring in human plasma

An HPLC method for the simultaneous determination of both caffeine and theophyllie in human plasma is described, using a reversed-phase chromatography column, heated by a thermostatic oven at 35°C, with UV detection and isocratic elution. The linearity and reproducibility of the method are verified. For the two drugs, the limit of detection is 0.1 μg ml⁻¹. This analytical method is rapid and reliable and allows routine controls of therapeutic levels of theophylline and caffeine, especially in premature infants where the volume of plasma samples is very small.