Pharmacokinetic profile of a new sustained-release theophylline pellet formulation for once-daily evening administration.

Euphylong is a new anhydrous theophylline sustained-release pellet formulation developed for once-daily administration in the evening in normal and slow metabolizers, and unequally divided twice-daily administration in fast metabolizers. Its pharmacokinetics have been investigated with respect to bioavailability, peak-trough fluctuation, nocturnal plateau profile, food effects, predictability and reproducibility between subjects and from day to day. To this end, 7 single-dose and 4 multiple-dose, randomized, cross-over studies were performed in a total of 168 healthy, normal, male volunteers. In order to match the dosage strengths of three reference products, capsules containing different amounts of pellets--also referred to as Euphylong pellets--have been used. Absolute bioavailability of theophylline from Euphylong was 88 and 100%, depending on the rate and the total dose of the intravenous reference infusions. Relative bioavailability ranged between 85 and 112%, depending on the reference formulations. The peak-trough fluctuation was reduced for Euphylong pellets in comparison with other once-daily theophyllines, by more than 30% in the case of a reference tablet. In contrast to another once-daily theophylline capsule, Euphylong pellets seem to be hardly affected by meals. Moreover, in view of the known variability of theophylline pharmacokinetics both between subjects and from day to day, the nocturnal plateau profile, which is characteristic of Euphylong, is extremely reproducible. The nocturnal excess is consistently 30-40% and the plateau time is consistently 11-12 h in normal metabolizers. The long nocturnal plateau profile together with the high reproducibility of Euphylong pharmacokinetics enable an easy and safe adjustment of the dose tailored to the needs of the individual patient. In addition, the time of the evening dose and its relationship to meals is not critical in the case of Euphylong pellets. Particularly patients presenting with nocturnal asthma, which is one of the major areas of theophylline therapy, should have a clinically relevant benefit from Euphylong.