Relation of oral dose of oxtriphylline to serum theophylline level.

Serum theophylline levels were studied in relation to oral doses of oxtriphylline in 30 patients with reversible airway obstruction. A wide scattering of levels was observed and was attributed to widely differing rates of metabolism of the drug. From the data obtained it was concluded that the most commonly prescribed daily dose of oxtriphylline, 800 mg, will produce a therapeutic level of theophylline in only about one quarter of patients. A daily starting dose of 15 to 20 mg/kg, however, will produce therapeutic levels in approximately one third of patients without significant toxic effects. Once the patient's conditions is stable the serum theophylline concentration should be measured; if it is subtherapeutic the dose of oxtriphylline should be increased slowly and the serum theophylline concentration remeasured until a level of 10 to 20 microgram/ml is achieved.