Theophylline dosing and theophylline level testing in a family practice population

Theophylline level testing enables the physician to monitor patients on theophylline and maintain benefit vs risk at an optimum ratio. This study consisted of a retrospective chart review of 53 patients who had a total of 103 serum theophylline level determinations (STLDs) over a 12-month period. The study was designed to look at reasons why physicians ordered STLDs and to what extent those results influenced subsequent theophylline prescribing. Findings showed that a large number of STLDs were ordered on asymptomatic patients with no recent dose change or initiation of therapy and no recent hospitalization or emergency room visit. The most common reason for ordering an STLD was presentation with symptoms or signs of asthma and no other recent events. On several occasions when low results were obtained, theophylline dosage was not increased. In some of these cases the patient's clinical presentation may have influenced the decision to maintain the same dosage. Use of erythromycin and smoking status were observed to affect theophylline clearance. Most physicians failed to document time of last theophylline dose, which hindered accurate interpretation of STLDs.