The chemists always determine that a great variety of shapes and sizes is available among medical tablets. The most common shape of the tablet is a circular body with flat or slightly convex sides. There are also rectangular, triangular and many other shapes in the case of the speciality tablets.
The preliminary consideration in selection of particular shapes and sizes of the tablets is essentially ethical. These dimensions should be such that the tablets prepared have a pleasing appearance. Similarly, the use of a tablet is also an important consideration. A tablet meant for making solutions will be required to dissolve as quickly as possible and so it should be as thin as possible. This will require a larger diameter than average tablets of the same weight. Tablets which are to be dissolved slowly in the mouth should be flat for convenience of the user and thick enough to have a lasting effect on which the efficiency of the tablet will depend. Similarly, tablets which have to be coated after compression must have a deep convex shape and be harder than other tablets. It is more convenient as thin edges as practicable since it is easier to cover a thin edge during the coating process.
In addition to the above considerations there can also be important technical reasons which may influence the selection of particular dimensions of the tablets. It is often found that the preparation of deep convex tablets is difficult. The density and compression ratio are the important factors.
The tablet technologists say that different pressures may be required for the compression of different shapes of tablets. The different shapes of tablets (as flat-faced or convex-faced etc.) show a variation in physical properties even when compressed with similar unit area pressure. The flat-faced tablets show a relatively greater strength than the convex-shaped tablets.