The present article was to review the evaluation system to quantify the bitterness of medicines and its suppression using the taste sensor, in order to realize the theoretical design of taste-masking formulations. The sensor responses obtained by the eight sensors allowed not only the quantitative evaluation of the bitterness of the substance but also the interpretation of the perception mechanism and the characteristics of the bitter substance by using a principal component analysis. Single or multi regression analysis using the selected factors as explanatory variables allowed us the quantitative evaluation of bitterness for basic drugs, and single, binary- and multiple-component amino acid solutions. The effects of a bitterness-receptor antagonist, lipoprotein (BMI-40) could be evaluated using bitter-sensitive sensor. Whereas the sweet-sensitive sensor was useful for prediction of suppressed bitterness by sweeteners. Finally the possibility of molecular imprinted polymer as a screening system for bitterness-suppression for targetted drug was demonstrated. Hopes are that this study will serve as a step that the taste sensor will be actively used for efficient and effective designing of bitterness masking formulation.

The purpose of this study was to evaluate the degrees of bitterness and sweetness of five commercially available preparations (1 granule (B) and 4 dry syrups (DS-1-DS-4)) of acetaminophen (APAP) when suspended in water by human gustatory sensation testing and drug release test. The drug release experiment was performed in distilled water as the release medium at 4, 25 and 37°. The amount of APAP released from each preparation increased with an increase in medium temperature. In the human gustatory sensation test, we evaluated the bitterness and sweetness, respectively, at two time points. First, we evaluated the tastes immediately after the suspension had been kept in the mouth for 5 seconds, which we termed “immediately taste”. The second time point was 15 seconds after the suspension was ejected from the mouth but the mouth was not rinsed with water, which we referred as “residual taste”.

In the gustatory sensation test, all preparations were found to be significantly masked against the bitterness, but DS-2 was not sufficiently masked against the immediate bitterness, as compared with other DS preparations. In addition, the rank order of continued sweetness tended to be DS-1≥DS-4≥DS-3>B=DS-2 in descending order. These results suggest that the masking of bitterness was probably due to the sweetness enhancement and the decreased dissolution of APAP.

In the previous study, we tried to improve the solubility of poorly water soluble drugs using the Pulse shock wave Dryer method with various carriers and showed that PVP was the optimal carrier¹⁾. In this study, we carried out the same experiment selecting Pranlukast hydrate (ONON) as a model drug and PVP C-15, Kollidon VA64, PVP K-30, Kollicoat IR and Kollidon CL-M as carriers to clarify the relationship between the dissolution property of the test agent and the kinds of PVP. Furthermore, we prepared a spray-dried product using the Kollidon VA64 system, which could optimally improve the dissolution property of the drug. Then the powder properties, such as specific surface area, amount of moisture adsorption, compressibility, granule strength, granule hardness of the products and tablet hardness obtained by a compression test were measured and compared between the two preparations.

As the result, the highly hygroscopic property was a major problem of the PVP system in general, but it was clearly demonstrated that the pulsed product using Kollidon VA64 as a carrier possessed lower hygroscopicity and surpassing dissolution property and compressibility. In addition, it was proven that the pulsed products, which formed smooth and heavy spheres, possessed good compressibility and that the powder was more easily pressed into tablets than the spray-dried products.

Based on the findings described above, we could improve the dissolution property of the drug by using Kollidon VA64 as the carrier; furthermore, it possesses surpassing powder properties.

A Terahertz (THz) wave has distinctive characteristics of high transmittance for many objects such as radio waves, and straight advancement such as ordinary light. Vibration spectra of weak intermolecular interactions such as hydrogen bonding and van der Waals' force can be detected in the THz region. Skeletal vibrations of the molecule and phonon modes of organic crystals also lie in this frequency band. Since THz spectra is sensitive to molecular structure and crystal formation, THz spectrometry is expected to be useful to detect deterioration or transformation of medicines (e.g. oxidation, hydration, crystal modification, isomerization). The high resolution and wide-frequency band of our spectrometer have considerable potential for molecular vibration analysis in the THz range.

We successfully applied THz spectroscopy to commercially available vitamin tablets provided from four manufacturers. THz spectrometry was able to recognize the manufacturer of each tablet. It could also be used for component analysis of medicine using the differential spectrum method and comparison with a database. For practical use, construction of a THz spectra database including all medicines and their contents is strongly needed at first. If the components of the medicine show polymorphism, like vitamin B₂, the medicine can be distinguished from other forms even though they have the same contents.