Effect of serum caffeine level on pneumocardiogram of premature infants treated for apnea with theophylline.

It is speculated that measurement of serum theophylline concentration alone, without concomitant caffeine level determination, may lead to a false negative (normal) pneumocardiogram due to possible existence of therapeutic caffeine level resulting from the methylation of theophylline. Treatment of neonatal apnea with theophylline as documented by a normal follow-up pneumocardiogram should be considered successful only when the levels of both theophylline and caffeine have been documented subtherapeutic at time of re-test.