Pharmacokinetics and pharmacodynamics of a short- and long-acting theophylline medication (theolair and Theolair retard) in normals and asthmatics. Part I: pharmacokinetics.

Plasma concentration and pharmacokinetic data of a sustained-release theophylline (Theolair retard) was compared with that of a short-acting theophylline (Theolair) in six normals and six patients with asthmatic bronchitis. Steady-state plasma levels were reached on day 4 or earlier for both Theolair retard and Theolair. Theolair retard showed stable plasma concentrations. Patients showed lower (maximal) values for the plasma levels for Theolair retard and for Theolair and a shorter elimination half-life time for Theolair. This may perhaps be explained by the larger number of smokers among the patients versus the normals. As for the large interindividual variation in plasma levels and pharmacokinetics it seems advisable to administer theophylline guided by plasma levels estimated on the 4th day of administration, about 3 h after the morning dose.