Journal of Pharmaceutical and Biomedical Analysis 62 (2012) 42–47 Contents lists available at SciVerse ScienceDirect Journal of Pharmaceutical and Biomedical Analysis j ourna l ho me p a ge: www.elsevier.com/locate/jpba Chiral recognition of dapoxetine enantiomers with methylated-gamma-cyclodextrin: A validated capillary electrophoresis method Gábor Neumajer a , Tamás Sohajda a,b , András Darcsi a , Gerg ˝ o Tóth a , Lajos Szente b , Béla Noszál a , Szabolcs Béni a,∗ a Semmelweis University, Department of Pharmaceutical Chemistry, H˝ ogyes Endre u. 9, Budapest H-1092, Hungary b CycloLab R&D Ltd, Illatos út 7, Budapest H-1097, Hungary a r t i c l e i n f o Article history: Received 11 November 2011 Received in revised form 23 December 2011 Accepted 24 December 2011 Available online 3 January 2012 Keywords: Priligy Enantioseparation Synthesis Orthogonal experimental design Validation a b s t r a c t The enantiomers of dapoxetine, a serotonin transporter inhibitor for the treatment of premature ejac- ulation have been separated by cyclodextrin modified capillary zone electrophoresis using uncoated fused-silica capillary. Over 20 cyclodextrins were screened as chiral selectors, investigating the stability of the inclusion complexes and enantioseparating properties. According to the preliminary experiments as chiral selector randomly methylated- -cyclodextrin was chosen. The basic chemical and instrumen- tal parameters of enantioseparation as concentration of buffer, chiral selector and organic additive, pH, temperature and applied voltage were optimized afterwards using an orthogonal experimental design. Using this methodology not only the optimal parameter values for chiral separation (15 ◦ C, +15 kV, 70 mM acetate, 20 v/v% MeOH, pH* = 4.5, 3 mM methylated- -CyD) but also the significance order of factors on resolution was determined. Applying these parameters an optimal resolution of 7.01 was achieved. The optimized method was then validated according to the ICH guideline Q2 (R1) with regard to repeatability, linearity range, LOD, LOQ, accuracy and robustness. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Premature ejaculation (PE) is the most common male sexual dis- order, and is estimated to affect up to 30% of men worldwide [1]. PE affects men of all ages equally from pubescent to elderly. Despite its high prevalence and well-known adverse effects on men’s life quality, only recently has attention been focused on developing therapeutic strategies. As treatment of the condition numerous non-pharmacological (e.g. psychological and behavioral therapy, self-help techniques, mechanical aids) and pharmacological (topi- cal anesthetics, selective serotonin reuptake inhibitors (SSRIs), type 5 phosphodiesterase inhibitors) approaches are in practice [2]. The potential of antidepressants to treat PE was first introduced by Ahlenius et al. in 1981 [3]. As SSRIs are intended for chronic use in the treatment of depression, they are designed to provide a con- stant systemic concentration with long-term administration and daily dosing. This application in the treatment of PE is associated with a number of undesirable side-effects, such as decreased libido and erectile dysfunction [4]. Therefore, an ideal SSRI compound Abbreviations: API, active pharmaceutical ingredient; BGE, background elec- trolyte; Dpx, dapoxetine; DS, degree of substitution; EtOAc, ethyl acetate; PE, premature ejaculation; SSRI, selective serotonin reuptake inhibitor. ∗ Corresponding author. Tel.: +36 1 217 0891; fax: +36 1 217 0891. E-mail addresses: beniszabi@gmail.com, beniszabi@gytk.sote.hu (S. Béni). treating PE should have rapid absorption and elimination to mini- mize the side-effects [5]. Dapoxetine (Dpx), (S)-N,N-dimethyl[3-(naphthalen-1-yloxy)- 1-phenylpropyl]amine hydrochloride, Priligy®) is a novel short acting selective serotonin reuptake inhibitor that is being devel- oped specifically as an on-demand oral treatment of PE with a unique physicochemical and pharmacokinetic profile [5]. Dpx attains its peak plasma concentration in about 1.5 h after dos- ing which is much faster than conventional SSRIs and by 24 h the plasma concentration decreases to approximately 5% of the peak concentration. These pharmacokinetic properties make Dpx an excellent candidate for on-demand dosing of PE. A wide range of synthetic procedures were developed to synthesize racemic and enantiopure Dpx [6–14]. The enantiomeric excess in these proce- dures were verified solely by chiral HPLC [8,11,13]. As the eutomer (S)-Dpx is 3.5 times more potent SSRI than (R)-Dpx [15] and most of the synthetic procedures bear the possibility of chiral contami- nation, a fast and reliable enantioseparating method is essential for the analysis of the compound. Moreover, this drug is also a target for adulteration as other active pharmaceutical ingredients (APIs) for the treatment of sexual disorders [16]. Enantiomeric purity and characterization of the enantiomers’ biological activity are crucial requirements for novel chiral drug candidates. Therefore, enantioselective analytical methods are necessary to control the enantiomeric purity of pharmaceuti- cal preparations. Undoubtedly, capillary electrophoresis has been 0731-7085/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.jpba.2011.12.032