The effect of rifampin on theophylline kinetics

The effect of rifampin on the pharmacokinetics of theophylline was studied in ten healthy nonsmoking men (age, 23-42 years). Each subject received 5.9-6.8 mg/kg of aminophylline intravenously over 20 minutes before and at the end of two weeks of oral rifampin therapy (600 mg/d). Theophylline serum concentrations were measured serially over the 24 hours following each aminophylline infusion. In every subject, rifampin caused an increase in total clearance (from 0.88 +/- 0.21 to 1.21 +/- 0.29 mL/min/kg) and terminal elimination rate constant (from 0.104 +/- 0.023 to 0.148 +/- 0.030 hr-1) and a decrease in the area under the theophylline concentration-time curve (from 104 +/- 29 to 76 +/- 19 hr-mg/L) and half-life of theophylline (from 7.0 +/- 1.7 to 4.8 +/- 0.9 hr). All of these changes were significant (P less than .02, Wilcoxon matched-pair, signed-rank, two-tailed test). The apparent volume of distribution of theophylline did not consistently change following rifampin administration (mean change, -4%; range, -18(-)+20%, P greater than .20). Patients should be monitored for signs of decreased theophylline efficacy when rifampin is added, or of increased theophylline toxicity when rifampin is discontinued from maintainance therapy.
CiteULike    Complore    Connotea    Del.icio.us    Digg    Reddit    Technorati    Twitter    What's this?