The Surface Hardness Distribution Over ‘Tiltab’ Tablets

Abstract

A modified microindentation apparatus is described and shown to be a satisfactory technique to monitor the surface hardness and resilience of tablets with unusual surface curvatures, in this case those associated with the SK&F novel tilting tablet concept. The indentation test has been able to pin-point differences in properties over the tablets and has demonstrated various trends in surface hardness for these new shapes. ‘Ridaura’ tablets, which are square, bevel edged with normal convex surfaces bearing a raised dome on both faces, show stronger surface characteristics around the periphery and lower surface hardness over the dome. The elastic quotient is also reduced at the top of the dome and this may well be due to the reduced consolidation in this region during compression. Two other tablet shapes were also examined: 200 mg and 800 mg ‘Tagamet’ tablets. The 200 mg tablet is a round shape similar in profile to the square ‘Ridaura’ product. There is a quantitative similarity between the data of both surfacers for this tablet with harder areas at the periphery, but unlike the ‘Ridaura’ it also demonstrates a measurable reducation in surface hardness and resilience at the peak of the tilt feature. The more complex oval 800 mg ‘Tagamet’ ‘Tiltab’ tablets have generally higher surface hardness and resilience. It is believed that a slightly modified formulation may also have contributed to these significantly higher volumes.

It is concluded that the microindentation apparatus may well be a useful tool to assist in the optimisation of formulations of ‘Tiltab’ tablets, as well as in determining the most appropriate processing conditions.