[Comparative study of plasma levels of 2 delayed-action theophyllines: Theostat 200 and Theodur 200, after a single evening dose].

Plasma levels of two slow-release theophylline preparations, Theostat 200 and Theodur 200, administered in one single evening dose during steady state were compared in a double-blind cross-over study involving 10 male volunteers (mean age: 52.3 +/- 7.5 years) with chronic obstructive lung disease and free from pathology or treatment that might have interfered with theophylline kinetics. Mean areas under the drug plasma concentration curves were 222 +/- 101 mg.h/l with Theostat 200 and 264 +/- 114 mg.h/l with Theodur 200. Mean percentages of fluctuation were 72 +/- 13 and 71 +/- 17 respectively (N.S.). The free fractions measured at peak level were higher with Theodur (9 +/- 2.9 mg/l) than with Theostat (7.1 +/- 2.4 mg/l) (P less than 0.05). While mean values were approximately the same with the two products, interindividual variations were pronounced, with several plasma levels of Theostat 200 in areas regarded as ineffective and several plasma levels of Theodur 200 in areas regarded as toxic. This type of preparation therefore is mostly useful to patients who would benefit from high plasma levels of theophylline in the early morning.