[Asthma patients requiring unusually high doses of theophylline]

We often see severe asthma attacks occur in patients taking high doses of theophylline and disappear soon after intravenous injection of aminophylline. Theophylline concentration in the serum was investigated in those cases. Twenty five asthmatic patients, 14 males and 11 females, 16-17 years of age, visited our out-patient clinic 41 times in total over a period of 9 months suffering from dyspneic attacks of such severity that they had difficulty in speaking and walking although they had taken at least 200 mg theophylline within 6 hours and 400 mg within 12 hours. All cases were treated with iv infusion of 2.8-14 ml of 2.5% aminophylline for 5-15 minutes until the dyspneic symptoms disappeared. Theophylline levels in the serum (micrograms/ml) before the treatment were 2.0 in 1 case, 6.0-9.8 in 8, 10-20 in 23, and over 20 in 9 cases. Levels after the treatment were 5.8 in 1 case, 10-20 in 15, and over 20 in 25 cases. In one patient, a 27-year-old female, 300-400 mg of theophylline, aminophylline, or choline theophyllinate tablets could increase theophylline concentration in the serum only 4.8 micrograms/ml or less, while her theophylline clearance was normal. The present study revealed that there are asthmatic patients requiring unusually high doses of theophylline, partly because some of them have problems in absorption of theophylline, and partly because many of them need higher levels of blood theophylline than those usually thought of as standard therapeutic concentrations.