Xanthine therapy results in improved clinical status of asthma

Purpose: We compared the clinical efficacy and safety of sustained-release theophylline, enprophylline and placebo in asthmatics. Methods: Investigators at 20 sites in North America entered 310 asthmatic patients into the 12 week trial. The initial dose of either active therapy was 150mg every 12 hours, and was increased to relieve respiratory symptoms as indicated. Serum levels were monitored by a separate physician at each site. The medication given, actual dose for the patient and serum levels were blinded to all other persons. The dose of each medication was adjusted depending on clinical criteria. The dose of theophylline was not increased if the serum level was found to be over 15mcg/ml. Evaluations consisted of periodic spirometry, assessment of status, patient evaluation of symptoms, daily peak flow measurements, and use of prn albuterol. Results: Optimal dosing for theophylline was generally 600 or 900 mg/day and for enprophylline was 900 or 1200 mg/day. Adverse events considered to be related to therapy occurred in 57% of theophylline, 63% of enprofylline and 35% of placebo patients. Significant improvements (p<0.05, ANOVA) in pulmonary function and clinical status were seen with both active drugs. No net decrease in numbers of puffs of albuterol was observed in the placebo group while significant decreases in the number of puffs were observed in the xanthine groups. Significant differences (p<0.05, chi-square) in clinical status after 12 weeks of therapy were observed for the xanthine treated patients. SYMPTOM CONTROL T E P Poor 0% 2% 13% Partial 22% 23% 25% Well or very well 78% 75% 62% T=theophylline (n=105), E=enprofylline (n=102), P=placebo (n=99) Conclusions: Xanthine therapy shifts the profile of treatment groups to better control of asthma symptoms, but with more side effects. The optimal dose of theophylline is generally 600 to 900 mg. Clinical Implications: If properly monitored, xanthine therapy may result in improved symptoms in asthma, especially if the patient feels that symptoms are poorly controlled.