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Pakistan Journal of Biological Sciences

Year: 2001  |  Volume: 4  |  Issue: 5  |  Page No.: 572 - 574

Binding of Dexamethasone Phosphate and Testosterone Phenyl Propionate to Bovine Serum Albumin: Drug?drug Interaction at the Binding Site

M. M. Rahman, A.B.S.M. Osman Gani, M.A. Choudhury and M.H. Rahman


The binding of dexamethasone phosphate (DP) and testosterone phenyl propionate, (TPP) two semisynthetic steroids, to bovine serum albumin (BSA) was studied by equilibrium dialysis method at 25°C and pH 7.4 with a view to have an insight into the competitive binding characteristics of these two drugs, when bound to BSA simultaneously. There was increase in free concentration of DP due to addition of TPP and vice versa during concurrent administration of these two drugs, thereby causing reduced binding of these two drugs to BSA. However, the free fraction was not increased up to a level as it was expected from direct competitive displacement. In absence of the site I specific probe (warfarin sodium), DP after being displaced by TPP or vice versa from its high affinity binding site (site II) rebound to its low affinity binding site (site I) on BSA. However, when the site I was sufficiently blocked by warfarin, the increment in the free concentration of the displaced drug was more prominent. This form of modified displacement has been referred to as site-to-site displacement.

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