RELATIONSHIP BETWEEN PROTEIN-BINDING AND FREE DRUG CONCENTRATIONS OF A SPARINGLY WATER-SOLUBLE SELECTIVE SEROTONIN REUPTAKE INHIBITORS (ESCITALOPRAM) AND ITS INTERACTION WITH ARSENIC

N. SUBHAN*, R. HABIBUR***, A. ASHRAFUL**, I. RASHEDUL***, R. MAHBUBUR****

*Department of Pharmacy, Khulna University, Khulna, Bangladesh, e-mail: rimmi04@yahoo.com
**Department of Pharmacy, Stamford University Bangladesh
***Department of Pharmaceutical Technology, Dhaka University, Dhaka, Bangladesh
****Department of Pharmacy, Jahangirnagar University, Savar, Dhaka, Bangladesh

Abstract. Escitalopram is the (S)-enantiomer of the racemic selective serotonin reuptake inhibitor antidepressant citalopram. Clinical studies have shown that escitalopram is effective and well tolerated in the treatment of depression and anxiety disorders. Single isomers of the selective serotonin reuptake inhibitors citalopram (escitalopram, S-citalopram) and fluoxetine (R-fluoxetine) are currently under development for the treatment of depression and other psychiatric disorders. Previous studies conducted in laboratory animals have revealed that the biological effects on serotonin reuptake for citalopram reside in the S enantiomer. In contrast, both enantiomers of fluoxetine contribute to its biological activity. The protein-binding of escitalopram was measured by equilibrium dialysis in the bovine serum albumin (BSA). Free escitalopram concentration was increased due to addition of arsenic which reduced the binding of the compounds to BSA. During concurrent administration, arsenic displaced escitalopram from its high-affinity binding Site I, and free concentration of escitalopram increased from 8.32% to 24.51% and 0.067% to 14.56% of Site I probe respectively. Thus, it can be ascribed that arsenic displaced escitalopram from its binding site resulting in an increase of the free escitalopram concentration in plasma. Potential correlation of these unique attributes of escitalopram and Arsenic are discussed.
Key words: Arsenic; escitalopram, bovine serum albumin, plasma protein binding, drug interaction, antidepressants, SSRIs.

Corresponding author’s e-mail: rimmi04@yahoo.com

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