BSc (Pharm)(Hons), PhD, National University of Singapore
Department of Pharmacy, National University of Singapore
18 Science Drive 4, Singapore 117543
Tel: +65 6516 2930
Fax: +65 6779 1554
Email: phapaulh@nus.edu.sg
Research Website
Teaching Activities in NUS
- PR3104 – Dosage Form Design IV
- PR4205 – Special Drug Delivery Systems
- PR5214 – Advances in Tablet Technology
Research Interests
My research is in the area of pharmaceutical technology, with emphasis in manufacturing processes and dosage form design. The main areas of work centre on compaction studies using universal testing machine and roller compactor, pelletisation by wet and melt methods, coating for colour and controlled drug delivery, and specialised delivery systems including transdermal and inhalation technologies.
The setting of GEA-NUS Pharmaceutical Processing Research Laboratory (PPRL) with substantial financial support from the National Science and Technology Board, National University of Singapore and private companies had helped tremendously in the establishment of a centre of excellence for pharmaceutical technology research in Singapore. The project collaborator, Dr Chan Lai Wah also played a pivotal role in the establishment and operation of GEA-NUS PPRL. GEA-NUS PPRL is today the leader in the fields of several manufacturing process research and product development in this region.
The research work in inhalation technology was presented at the 10th International Pharmaceutical Technology Symposium in Istanbul, Turkey, 11-13 September, 2000. The research on “Rugosity Effects of Carriers on the In Vitro Inhalation Drug Deposition Profiles” carried out by the post-graduate student Lim Liang Theng won the best poster award. Liang Theng’s research work revolves around the measurement of surface roughness by scanning probe microscopy and evaluation of the effects of roughness on drug particle adhesion in the development of inhalation products.
Other research highlights include the development of a spot colour analysis method for pellets by post-graduate student Chan Wai Yee. This would enable the determination of colour coating uniformity by measurement of the colour distribution of individual pellets. The method of measurement developed is currently being used to evaluate the efficiencies of pellet coating equipment.
In the areas of controlled drug delivery systems, the effect of particle size and size distribution of hydrophilic diffusion barrier polymer particles on the formation of matrices by compaction and their influence on drug release are being investigated. The factors governing matrix compaction and the relationship between particle properties and drug release from matrices are established. The application of roller compaction the preparation of drug matrices is also under investigation.
A significant amount of research work has been carried out in the area of pelletisation. Pellets are produced by both melt and wet methods. In melt pelletisation, pellets are produced by in situ melting of binder particles during high shear processing. Highly spherical pellets were produced using both hydrophilic and hydrophobic meltable binders. In wet pelletisation, the production of pellets by extrusion spheronisation and rotary processing are being studied. As microcrystalline cellulose is an essential component in wet spheronisation, the mode of action of microcrystalline cellulose was investigated. It was found that interparticulate and intraparticulate voids greater than 10 mm play an important role in determining the amount of water retained within the agglomerate during extrusion-spheronisation and microcrystalline cellulose acted as a spheronising aid by its ability to be a water repository with properties of a crystalline sponge.
GEA-NUS PPRL has also undertaken a number of projects with private companies and research centres. These projects, which focus on product development, are on going.