Study of theophylline metabolism in premature human newborns using stable isotope labelling.

A new metabolic pathway of theophylline has been investigated in premature human newborns using the ion cluster technique of stable isotope labelling combined with gas chromatography mass spectrometry. Labelled caffeine, paraxanthine and theobromine have been found in plasma and urine of two preterm newborns receiving [1,3-15N], [2-13C] theophylline for the treatment of primitive apneas. Theophylline is converted to caffeine by N-7 methylation. In adults, the inverse process exists wherein caffeine is demethylated to give theophylline.