Issue link: https://www.e-digitaleditions.com/i/1349974
44 March/April 2021 Tablets & Capsules Product Polymer Plasticizer Opacifier % solids in water Typical weight gain Talc free Cost effective Processing efficiency Stability on typical multivitamin Brightness/ appearance SheffCoat TF 30751440 HPMC PEG Calcium carbonate 15 3-5% + • • • SheffCoat TF 30748439 HPMC Triacetin Calcium carbonate 15 3-5% x + • • • SheffCoat TF 30739258 HPMC MCT Calcium carbonate 15 3-5% + • • • SheffCoat TF 30748441 HPMC/HPC MCT Calcium carbonate 13 3-5% x • • + • SheffCoat TF 30748516 HPMC/HPC n/a Calcium carbonate 13 3-5% x • • + • SheffCoat TF 30748443 HPMC/ PVA/HPC n/a Calcium carbonate 18 3-5% x • + • • SheffCoat TF 30753411 HPMC MCT Calcium carbonate/ isomalt 20 3-5% x + + • + SheffCoat TF 30754601 PVA PEG Calcium carbonate 20 4-6% x + + • • Table 1 TiO 2 replacement formulations for scuffing than calcium carbonate because it is a little more abrasive. Between these three options, and working with your coating manufac- turer, you can most likely achieve an acceptable coating without using TiO 2 . However, be aware that when you replace TiO 2 with one of these alternative opacifiers, depending on the pigment and the tablet core itself, you will likely need to increase the weight gain and/or adjust the coating parameters during coating to achieve the same tablet appearance. Table 1 shows some examples of the SheffCoat TF family of TiO 2 -free film coatings developed by Kerry. These formulas are typically applied as an aqueous dispersion containing between 12 and 20 percent solids, depending on the type and amount of polymer. Pro- cessing conditions, such as dispersion time, spray rate, and inlet and tablet bed temperatures should remain in the same ranges as with coatings that con- tain TiO 2 but may require adjustments see gray scuff marks, which are caused by a reaction between the TiO 2 and the oxidation on stainless-steel coating pans. With calcium carbonate coatings, there is a lower risk of scuff marks. Some forms of calcium carbonate are also suitable as de-tackifiers. Another option that offers some benefits is isomalt, which is mostly used as a filler-binder and a sug- ar-free sweetener. In addition to some opacifying properties, isomalt has a brightening effect. We've found that adding a small amount of isomalt along with calcium carbonate may provide a brighter, whiter finish than some stan- dard TiO 2 -containing film coatings. Working with your coating manufac- turer is key to ensuring an exact and consistent color match to an existing TiO 2 coating. We have also evaluated tricalcium phosphate as a TiO 2 replacement, but the opacity was not as good as with calcium carbonate. Also, trical- cium phosphate has a higher potential depends on the core's initial appear- ance as well as its shape and size. In addition to excellent opacity, TiO 2 is very heat and light stable, whereas other so-called opacifiers tend to be more sensitive to heat and light. This makes replacing TiO 2 in film coatings challenging. There are options, however, that can produce white tablets and can also be mixed with other pigments as previously noted to achieve a range of colors. We've discovered that calcium car- bonate is a very good option to replace TiO 2 . Not every grade of calcium car- bonate provides the same opacity level, however, so it is important that the coating manufacturer works hand in hand with the tablet manufacturer to select the appropriate TiO 2 replace- ment and coating formulation. While TiO 2 -containing coatings offer unparalleled whiteness and opac- ity, there are some benefits to be had by using alternatives. For example, sometimes on white tablets you might