Dr Waseem Kaialy

Faculty of Science & Engineering

Dr Waseem is a pharmacist since 2007, following his graduation from Damascus University with the top student honour and five academic excellence awards. He completed his PhD in 2013 in Medway School of Pharmacy at University of Kent. The work involved pharmaceutical particle engineering for enhanced drug delivery to the lung.

Waseem is an associate member of Royal Pharmaceutical Society. He has an extensive experience and a proven track record in the field of formulation development of pharmaceutical drug delivery. His ongoing research topics include particle engineering of excipients and drugs in order to improve their physicomechanical and physicochemical properties for better drug delivery.

Xylitol: a potential alterative pharmaceutical excipient in the production of pharmaceutical tablets

Introduction

Xylitol is a five-carbon sugar alcohol that can be found in food sources such as berries and mushrooms, etc. Xylitol is an attractive excipient for oral drug delivery because it has a similar degree of sweetness to that of sucrose; however, xylitol has a positive role in the health of patients as a sweetener. Unlike sucrose, xylitol has a low ‘glycaemic index’ and, therefore, it is metabolized largely, even without insulin, so it can be safely consumed by non-insulin dependent diabetics as well as the obese (1). Technological advantages of xylitol include its good taste profile as well as the production of a pleasant cooling effect in the mouth, which is highly effective to mask the unpleasant flavors associated with some drugs and excipients (2).Despite being an attractive excipient, xylitol has poor compactibility and compressibility that make it unsuitable for tableting via the direct compression (3).

Aims

This study was performed to improve the compactibility and the pharmaceutical performance of xylitol by improving its physicomechanical properties to make it better suited for tableting using direct compression, without compromising its chemical structure or stable polymorphic form.                                                                   

Methods

Antisolvent crystallization technique was employed in the presence of various additives, i.e., polyethylene glycol (PEG), polyvinylpyrrolidone (PVP) and polyvinyl alcohol (PVA₂₂₀₀₀ or PVA₁₆₀₀₀) at varying concentrations (0.06%, 0.3%, 0.6% and 1.2%, w/v). The size and morphological changes (of xylitol) induced by crystallization in the presence of the additives were studied. The dissolution performances of tablets comprised of crystallized xylitols formulated with a model poorly water-soluble drug, i.e., indomethacin, in comparison to commercial xylitol were also evaluated.

Summary findings

Crystallized xylitols, having the desired polymorph, which produced significant improvement in mechanical strength of tablets and dissolution behaviour of poorly water-soluble indomethacin, were successfully engineered by antisolvent crystallization technique in the presence of various hydrophilic additives. The crystallized xylitols demonstrated improved pharmaceutical performance in comparison to commercial xylitol and commercial mannitol. The type of additive used during crystallization was a key optimization factor. Xylitol crystallized without additive and xylitols crystallized in the presence of polyvinylpyrrolidone or polyvinyl alcohol demonstrated improvement in hardness of directly compressed tablets; however, such improvement was not seen for xylitols crystallized in the presence of PEG. The higher the concentration of PVP used during crystallization the stronger were the tablets produced. The dissolution rate and efficiency of indomethacin increased linearly with the concentration of PVA or PVP used during crystallization of xylitol. Commercial xylitol produced the weakest tablet mechanical strength and the poorest dissolution behaviour of indomethacin.

References

1. De Faveri D, Perego P, Converti A, Del Borghi M. Xylitol recovery by crystallization from synthetic solutions and fermented hemicellulose hydrolyzates. ChemEng J 2002;90(3):291-298.
2. Williams L. Wilkins and Handbook of Pharmaceutical Excipients (Rowe et al., eds). 2003.
3. Sjökvist E, Nyström C. Physicochemical aspects of drug release. XI. Tableting properties of solid dispersions, using xylitol as carrier material. Int J Pharm 1991;67(2):139-153.