title: Circadian variation in plasma theophylline concentrations during maintenance therapy with a sustained-release preparation in patients with obstructive airways disease.
abstract: Circadian variation in plasma theophylline concentrations was studied in eight patients with obstructive airways disease during regular 12-hourly dosing at 09.00 and 21.00 h with a sustained-release theophylline formulation. After regular dosing for a minimum period of 3 days, plasma concentration measurements were made at 09.00, 13.00, 21.00 and 01.00 h on 3 consecutive days and at more regular intervals during a complete 24 h period on day 4. On each day, theophylline concentrations for the first 4 h of the dosing interval were consistently higher during the day than at night. However, the differences were significant only at 13.00/01.00 h on day 2, and for each of the first 4 h on day 4. On day 4, following the dose at 21.00 h the mean peak plasma theophylline concentration occurred 6.9 +/- 0.8 h after dosing; in contrast, after the morning dose the mean peak concentration occurred at 4.5 +/- 0.8 h. However, the mean 'steady-state' concentrations during the two dose intervals were not significantly different. Thus circadian variations in plasma drug concentrations do occur in patients taking maintenance theophylline therapy: differing rates of absorption may account for the observed pattern.
mesh_terms: D000368:Aged; D002940:Circadian Rhythm; D003692:Delayed-Action Preparations; D005260:Female; D006801:Humans; D008173:Lung Diseases, Obstructive / Q000097:blood* / Q000188:drug therapy; D008297:Male; D008875:Middle Aged; D013806:Theophylline / Q000008:administration & dosage / Q000097:blood* / Q000627:therapeutic use
chemical_list: D003692:Delayed-Action Preparations; D013806:Theophylline