Population pharmacokinetic analysis of theophylline: Relationship between serum concentrations and clinical effects in therapeutic drug monitoring

Therapeutic drug monitoring (TDM) of theophylline is essential duties at ho spital pharmacy in Japan. The relationship between serum concentrations and clinical effects of theophylline has been investigated The pharmacokinetic s of theophylline was determined from the concentration of theophylline in the serum which were calculated on the basis of TDM for patients administer ed theophylline. The one-compartment model as a pharmacokinetic model was a ssumed. The relationship between clinical effects of theophylline and the p redicted concentrations calculated using population parameters was evaluate d. The obtained parameters are ka(h(-1))=0.223, ke(h(-1)) =0.047(1-0.0025.a ge(y) (p.o.) and 0.076(1-0.0025 age(y)) (d.i.v.), Vd(1/kg) =0.733 (p.o.) an d 0.830 (d.i.v.). The bioavailability is 0.732, and theophylline/aminophyll ine is 0.846. The model including no serum creatinine as a variational fact or was considered to be best. The following three groups were used as a cli nical evaluation; effective as theophylline therapy was 43%, no change of t he clinical status after administration of theophylline was 42%, and aggrav ation after administration of theophylline was 15%. There is no relationshi p between the predicted concentration using parameters of the final model a nd these three groups. These results suggest that TDM of theophylline shoul d be assessed in terms of clinical effects and also suggests that in should be kept monitoring from the viewpoint of the prevention of toxic effects i n the theophylline therapy.