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10 September 2020 Tablets & Capsules tablets, you may need to reduce the land width to make it proportional to the tablet size [2]. Two factors come into play. First, the edge volume of material lost from dedusting increases for a given land width as the tablet size gets smaller. Second, for tablets with deep cup pro- files, tablet ejection becomes more difficult as the tab- let becomes smaller because the cup angle—the angle between the cup and the land at their intersection— becomes steeper. Table 3 shows how tablet size and land width affect friability and cup angle for minitablets with a deep, con- vex cup profile. While you might think that a larger land width would decrease friability due to increased tablet hardness at the land, as the table shows, the friability advantage provided by a deeper cup is lost when the land width isn't proportional to the tablet size. In addition to the formulation characteristics and tab- let design, several tablet press settings and options are important to consider when manufacturing minitablets. These considerations will help to ensure that the formula- tion adequately fills the die cavities, that the tablets eject properly from the die cavity without damage, and that the microtip tooling is protected from damage due to excessive compression force. Ensuring adequate fill A tablet press fills formulation into the die cavities using a combination of gravity, feeder paddles (for power feeders), and the vacuum pressure created by the retrac- tion of the lower punch tip pulling the material into the die bore. When producing minitablets, minimizing the fill-cam depth helps control tablet weight, improve yields, and maintain content uniformity. It also allows the lower punch tip's design to be maximized for strength, which I will discuss later. A fill cam depth of 6 millime- A common Heckel plot simplifies to ln(1/E) versus P to plot K, where E (porosity) is 1 − D. The slope of the linear regression is the Heckel constant. Larger values indicate better plastic deformation at low pressures than do lower values [3]. Tablet design Tablet shape. Minitablets are most often round because round tablets are easier to eject and film coat than other shapes. Also, round punch tips are stronger for any given tablet size than other shapes. Other minitablet shapes include capsule, modified capsule, rectangular, bean-shaped, and oval. While you can coat modified-capsule- and oval- shaped minitablets, capsule-shaped and rectangular minitablets tend to suffer from twinning during film coat- ing, which is when the tablets' flat sides stick together. In applications where the minitablets are inserted into implantable silicone tubes for targeted release, rectan- gular tablets can maximize volume, but their small cor- ner radii increase the risk of dies cracking during com- pression. Bean-shaped tablets are generally impractical because of the increased tooling costs. Cup profile. Cup profile affects a tablet's surface area, overall thickness, and sideband (or belly band) thickness. Many tablet presses are limited in how close the upper and lower punch tips can be during compres- sion, so the tablet sideband must be a thickness that your machine can achieve while also providing the tar- get tablet weight. Table 1 shows a range of cup profiles used for minitablets. Table 2 shows a comparison of cup profiles and tab- let dimensions for 10-milligram, 2.5-millimeter- diameter minitablets. The Tableting Specification Manual provides minimum land-width values for conventional tablets, but for mini- Cup profile Cup depth (mm) Tablet thickness (mm) Sideband thickness (mm) Tablet surface area (mm 2 ) Flat 0 1.772 1.772 23.735 Flat face bevel edge 0.14 1.854 1.574 22.618 Flat face radius edge 0.14 1.868 1.588 22.615 Whisper face (lozenge) 0.225 1.913 1.463 22.291 Standard convex 0.35 2.154 1.454 22.007 Compound radii 0.44 2.223 1.343 21.828 Modified ball 0.82 2.662 1.022 22.069 Table 2 Comparison of cup profiles and tablet dimensions for minitablets Tablet weight = 10 milligrams Tablet diameter = 2.5 millimeters Compressed density = 1.15 mg/ml Tablet volume = 8.696 mm 3