[Monitoring of three delayed-release preparations of theophylline in the plasma of children: pharmacokinetic parameters and therapeutic significance].

The pharmacokinetic and clinical efficacy of three theophylline slow-release formulations was studied in 29 children suffering chronic bronchial asthma. Theophylline loading dose was of 6 mg/kg; maintenance dose was adjusted according to therapeutic effect and drug plasma concentrations and ranged to 11.1 to 31.3 mg/kg/daily (means = 22.32 +/- 6.6 mg/kg/daily). Peak theophylline plasma levels were 13.38 +/- 4.83 micrograms/ml and through plasma levels were 8.73 +/- 3.78 micrograms/ml. No difference was found among theophylline formulations for clinical response nor kinetic parameters. Drug plasma half-life varied from 2.9 to 18.2 hr (means = 8.85 +/- 3.64 hr). Theophylline total body clearance and apparent volume of distribution exhibited a marked decrease during chronic drug administration in relation to the values observed after intake of the loading dose. Twenty three of the children reached a good degree of control of bronchospasm and did not require any associated medication.