[Theophylline blood levels after administration of Euphyllin retard (author's transl)].

The plasma theophylline concentration gradually increases after oral administration of Euphyllin retard, followed by a slower fall, than is the case after Euphyllin tablets have been taken, in which case maximal theophylline levels are reached 1 1/2 hours after administration. When Euphyllin retard is given, one to two tablets (350-700 mg) eight or twelve hours apart, there is a progressive rise of theophylline plasma levels to a plateau. This plateau can be maintained and is dependent upon dosage and the half-life of theophylline, which varies amongst individuals. Patients with obstructive airway disease treated with one tablet of Euphyllin retard every twelve hours for several weeks had a mean plasma theophylline level of about 6 microng/ml. In these patients the airway resistance, measured by body-plethysmography, improved by about 30%, without any side-effects. Six and twelve hours after administration of two tablets of Euphyllin retard the mean plasma concentration was 13 and 9 microng/ml, respectively. About half the patients receiving the larger dose of two tablets every twelve hours had gastro-intestinal or CNS disturbances. Long-term administration of Euphyllin retard provides a constant blood level of the drug.