[Importance of the formulation for a chronopharmacologically optimised way of pain therapy. Results of a comparative bioavailability study of tramadol extended-release capsules after single-dose evening versus morning administration].

Unlabelled: Objective of this study was to investigate the rate and extent of tramadol bioavailability following evening versus morning administration.

Methods: The study was performed following an open, randomised, cross-over study-design. 18 male and female volunteers were enrolled into the study and treated with 200 mg tramadol extended-release capsules (T-long), which were to be taken either in the morning or in the evening.

Results: Plasma concentration versus time profiles obtained after morning and evening administration were almost superimposable for both, tramadol and its active metabolite. Maximum exposure of tramadol and O-desmethyltramadol (geometric means of c(max)-values) as well as extent of exposure (geometric means of AUC(0-48)-values) were comparable after morning and eveningadministration.

Conclusions: Time-point of administration does not have any relevant impact on the rate and extent of absorption in the investigated dosage form. Thus, time-point of administration may be adjusted to the patient's need in a chronopharmacologically optimised way for pain therapy.