Formulation and process engineering of freeze-dried orally disintegrating tablets

  • Rhys Jones

Student thesis: Doctoral ThesisDoctor of Philosophy


Orally disintegrating tablets (ODTs) which are also referred to as orodispersible and fast disintegrating tablets, are solid oral dosage forms which upon placing on the tongue, disperse/disintegrate rapidly before being swallowed as a suspension or solution. ODTs are therefore easier and more convenient to administer than
conventional tablets and are particularly beneficial for paediatric and geriatric patients,
who generally have difficulty swallowing their medication.
The work presented in this thesis involved the formulation and process development of
ODTs, prepared using freeze-drying. Gelatin is one of the principal excipients used in
the formulation of freeze-dried ODTs. One of the studies presented in this thesis
investigated the potential modification of the properties of this excipient, in order to
improve the performance of the tablets. As gelatin is derived from animal sources, a number of ethical issues surround its use as an excipient in pharmaceutical
preparations. This was one of the motivations, Methocel™ and Kollicoat® IR were evaluated as binders as alternative materials to gelatin. Polyox™ was also evaluated as a binder together with its potential uses as a viscosity increasing and mucoadhesive
agent to increase the retention of tablets in the mouth to encourage pre-gastric absorption of active pharmaceutical ingredients (APIs). The in vitro oral retention of
freeze-dried ODT formulations was one property which was assessed in a design of experiments – factorial design study, which was carried out to further understand the role that formulation excipients have on the properties of the tablets. Finally, the novel
approach of incorporating polymeric nanoparticles in freeze-dried ODTs was
investigated, to study if the release profile of APIs could be modified, which could improve their therapeutic effect. The results from these studies demonstrated that the properties of gelatin-based
formulations can be modified by adjusting pH and ionic strength. Adjustment of formulation pH has shown to significantly reduce tablet disintegration time. Evaluating
Methocel™, in particular low viscosity grades, and Kollicoat® IR as binders has shown that these polymers can form tablets of satisfactory hardness and disintegration time. Investigating Polyox™ as an excipient in freeze-dried ODT formulations revealed that low viscosity grades appear suitable as binders whilst higher viscosity grades could
potentially be utilised as viscosity increasing and mucoadhesive agents. The design of experiments – factorial design study revealed the influence of individual excipients in a formulation mix on resultant tablet properties and in vitro oral retention of APIs. Novel
methods have been developed, which allows the incorporation of polymeric nanoparticles in situ in freeze-dried ODT formulations, which allows the modification of
the release profile of APIs.
Date of Award3 Jun 2013
Original languageEnglish
SupervisorAfzal-Ur-Rahman Mohammed (Supervisor) & Yvonne Perrie (Supervisor)


  • lyophilisation
  • excipients
  • oral retention
  • nanoparticles
  • sustained release

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