Bioequivalence and Bioavailability Forum

Dear all,

I have one query regarding steady state bio equivalence study of Tramadol SR 200 mg tablets.

In public assessment report of Tramadol in which post-dose 12 hours sample was taken on day 1 to 4.

link: http://www.mhra.gov.uk/home/groups/par/documents/websiteresources/con140629.pdf

Also a bioequivalence study done in India; 12 hours post dose sample was collected on day 1 to 4. (Comparative bioequivalence studies of tramadol hydrochloride sustained-release 200 mg tablets - Accutest, India)

I want to know that what is significance of 12 hours post dose sample collection on day 1 to 4.

However guidelines states that “In multiple-dose studies, the pre-dose sample should be taken imme­di­ately before (within 5 min­utes) dosing and the last sample is recommended to be taken within 10 min­utes of the nominal time for the dosage interval to ensure an accurate determination of AUC_(0–τ).”

I want to understand that why 12 hours post dose sample was collected from day 1 to 4.