title: Is circadian variation in theophylline trough serum concentrations determined by time of dosing?
abstract: Ten healthy volunteers were each given two separate courses of eight doses of theophylline 200 mg as a slow release preparation at 12 hourly intervals. In the first course (regimen 1) the dose was given at 11.00 h and 23.00 h and in the second (regimen 2) at 05.00 h and 17.00 h. Sixty hours after the start of each course, four consecutive trough serum theophylline concentrations were measured. On regimen 1 the trough concentration of theophylline was 6.2 +/- 2.2 mg/l (mean +/- s.d.) at 11.00 h compared with 5.4 +/- 1.9 mg/l at 23.00 h (P less than 0.01). This circadian variation was abolished during regimen 2 when the mean theophylline concentrations were identical at 5.2 mg/l. The higher trough concentrations after the evening dose on regimen 1 and the loss of circadian variation on regimen 2 may be due to the change in sleep period in relation to the time of dosing.
mesh_terms: D002940:Circadian Rhythm; D004334:Drug Administration Schedule; D005260:Female; D006801:Humans; D007700:Kinetics; D008297:Male; D012890:Sleep; D013806:Theophylline / Q000008:administration & dosage / Q000097:blood*; D013997:Time Factors
chemical_list: D013806:Theophylline