Toxicokinetics of caffeine elimination in an infant

The kinetics of caffeine elimination were followed in a ten month old female acutely intoxicated on a street form of the drug. Urine drug screening by gas chromatography-mass spectrometry also showed the presence of ephedrine, phenylpropanolamine, caffeine, theophylline and theobromine. Blood analyses using high pressure liquid chromatography gave evidence for the presence of theobromine, theophylline, caffeine and 1,7-dimethylxanthine. Sequentially taken blood samples determined that the initial stage of caffeine elimination was nonlinear. The Vmax = 27.6 micrograms/ml/hr and Km = 284.6 micrograms/ml. At a plasma level of approximately 30 micrograms/ml the elimination became first order with ke = 0.097 hr-1 and t 1/2 = 7.1 hr. The metabolic generation of theophylline and its elimination were also studied. Theophylline ke = 0.069 hr-1 and t 1/2 = 10.0 hr. Elimination of both drugs was anomalously long for a child of this age.