A single-dose comparison of three slow-release theophylline oral preparations in healthy Thai volunteers.
The study was done to compare the pharmacokinetic characteristics of three slow-release theophylline (SRT) preparations. Twelve healthy nonsmokers were randomly assigned a single dose of the following treatments at weekly intervals: Theo-Dur, Theo-24 or Xanthium orally, or aminophylline intravenously. Serially collected serum samples were analyzed for theophylline with use of fluorescence polarization immunoassay (FPIA). All three SRT preparations showed reliable absorption characteristics, but Theo-Dur had a shorter Tmax and MRT and a higher Ka. The pharmacokinetic characteristics of Theo-24 and Xanthium were similar except that Xanthium had lower bioavailability. Using single dose data for simulation of steady state pharmacokinetics, we found that a once-a-day dosage regimen with either Theo-24 or Xanthium would maintain serum levels within the therapeutic range for average non-smoking young adults whereas more frequent dosing intervals with Theo-Dur would be more appropriate. Our results argue against open substitution of SRT preparations without, close monitoring of the serum theophylline concentrations when a change is made.
Kanthawatana
S
S
Department of Pharmacology, Chiang Mai University Faculty of Medicine, Thailand.
Tontayapiwat
A
A
Tonsuwannont
W
W
Manorot
M
M
D000284:Administration, Oral; D000328:Adult; D019540:Area Under Curve; D003692:Delayed-Action Preparations; D005260:Female; D006801:Humans; D008297:Male; D013785:Thailand; D013806:Theophylline / Q000008:administration & dosage / Q000493:pharmacokinetics*
D003692:Delayed-Action Preparations; D013806:Theophylline