The purpose of this study was to evaluate the accuracy of the recommended
theophylline therapeutic range in the treatment of acute
airway obstruction. Twenty seven patients (20 to 64 years) with acute
asthma attack were given
aminophylline intravenously to obtain a
theophylline concentration between 10 and 20 micrograms/ml. Peak expiratory flow rates (PEFR) and serum
theophylline concentrations were measured before and after
aminophylline injection. When a marked improvement was not seen after
aminophylline injection, the treatment was followed by inhalation of a beta-agonist and intravenously administered
hydrocortisone. In order to clarify the relationship between
theophylline efficacy at a therapeutic level and PEFR, as measured before
aminophylline administration, the patients were classified into four groups. Group A (n = 7):
asthma attack persisted regardless of treatment with
aminophylline, beta-agonist and
hydrocortisone, group B (n = 7):
asthma attack improved by
aminophylline, beta-agonist and
hydrocortisone, group C (n = 6):
asthma attack improved by both
aminophylline and beta-agonist, group D (n = 7):
asthma attack improved by intravenous
aminophylline alone. The means (+/- S.E.) PEFR before
aminophylline administration were 94.3 +/- 11.31/min in group A, 114.3 +/- 10.01/min in group B, 196.7 +/- 22.21/min in group C, and 220.0 +/- 12.51/min in group D, respectively. There were significant differences in PEFR between the A and C, A and D, B and C, and B and D groups. These findings suggest that
theophylline efficacy is not expected in patients with low PEFR (less than 2001/min) at the time of treatment of an attack, even if a therapeutic
theophylline concentration was obtained.