[Long-term stability of morning serum theophylline level in asthma patients under minimally 1-year therapy with Euphylong].

The long-term stability of morning serum theophylline concentrations (STC) and peak expiratory flow (PEF) was investigated for at least one year in 21 asthmatic patients who received individualised theophylline doses in addition to a baseline medication (beta 2-agonists, corticosteroids, anticholinergics by MDI). All patients had previously participated in a randomised crossover study with the new sustained-release theophylline formulation Euphylong, so that 24-hour steady-state STC profiles were available. During the 15 (13-18) months' follow-up, the theophylline dose was increased by about 6% on average; the largest increase of 33% (from 750 mg to 1000 mg) occurred in 4 patients. The morning STCs between 8 and 9 a.m. were intra-individually averaged over the longest interval with a constant dose; median and range were 11.6 (9.7-15.8) mg/l. The coefficient of variation was less than 10% in 8 patients and between 11 and 20% in 10 patients. The corresponding peak-flow values were 474 (239-622) l/min with a coefficient of variation of up to 10% in 16 patients and between 11 and 20% in 3 patients. The long-term study over more than one year confirmed the reproducibility of the Euphylong plateau profile previously found in controlled short-term pharmacokinetic studies and clinical trials.