Treatment of Theophylline Poisoning

To the Editor.— We were interested in the report by Shannon and co-workers1 in which they described the use of multiple exchange transfusions for the treatment of an accidental toxic serum theophylline level in an infant in the postoperative phase of an arterial switch procedure. Although we have no problem with the rationale used for an invasive procedure that has multiple complication risks, we would like to emphasize the option for the use of activated charcoal products in infants who are able to tolerate orally administered medications.

Letter to the Editor

We thank Walker and Middelkamp for sharing their experiences. We also would like to emphasize Weinberger's point that when nausea, vomiting, or headache are present in nonwheezing children, additional theophylline administration should always be withheld until a serum theophylline level is measured. Theophylline continues to be very effective in the treatment of chronic asthma, and its use is to be encouraged. However, for optimal benefits with minimal risks, serum theophylline determinations must be rapidly obtainable.

Individualization of Theophylline Dosage Using a Single Serum Sample Following a Test Dose

Because formulas for theophylline requirement based on weight alone carry the risk of overdosing and toxicity, this study was designed to test a clearance nomogram for determining daily theophylline requirement after a known initial dose of theophylline. Twenty asthmatic children who had not taken theophylline for at least 36 hours fasted and were given one dose of anhydrous theophylline (5 mg/kg). Six hours later the serum level was measured and the appropriate dosage of sustained-release theophylline to achieve a serum level of 10 µg/ml was selected from the clearance nomogram. Three to seven days later a six-hour theophylline level was obtained. Of 20 patients, therapeutic levels of 10 to 20 µg/ml were achieved in 15, and the remaining five patients had levels close to this (range 6.2 to 16.0 µg/ml). The dosage requirement per 24 hours ranged from 10 to 32 mg/kg/24 hr. This method of determining theophylline requirements for children required measurement of the serum theophylline level only once for the determination of a safe and effective daily dose. It is especially valuable when follow-up is difficult and is a safe way to avoid serious overdosing while being certain of effective dosing.

Salivary and Urine Theophylline Levels in Management of Childhood Asthma

It is not possible to predict the plasma theophylline levels that can be achieved using slow-release aminophylline based on body weight or surface area. Improvement in FEV1 is directly related to increasing serum theophylline level, justifying the need for measuring levels in order to optimize therapy. As repeated venesection in children is unpleasant we have studied a simple method using saliva. Simultaneous blood and salivary theophylline levels correlated sufficiently well for salivary levels to be used for monitoring purposes. Urine levels did not correlate as well, but could be used for checking compliance.