Issue link: https://www.e-digitaleditions.com/i/962670
24 April 2018 Tablets & Capsules unpleasant to patients or when the dosage form has a high degree of interaction with patients' taste buds (such as with chewable and orally disintegrating tablets, gums, and gummies), taste masking is likely to be beneficial. For the formulator, the key initial consideration is the level of masking required, which depends on the API and the dosage form design. In some cases, the API is only slightly bitter and can be masked easily with flavors and sweeteners; in other cases, the API has a very bitter taste requiring additional taste-masking techniques. For general use tablets, which the patient swallows whole, an immediate-release film coating is typically sufficient to mask an unpleasant API. With bitter APIs, however, even a small amount of exposure is sufficient to give the patient a perception of bad taste. In these cases, formulators should consider using a barrier membrane coating or other alternative technique to mask the taste of the drug particles or granules. Dosage strength may dictate whether a specific taste- masking formulation strategy is suitable. Low-dose APIs are easiest to mask, while high-dose APIs pose a problem simply because more material (and a greater surface area) needs to be masked. This is especially true for formulations with fast-dissolving bases, which may leave patients with a mouthful of coated API particles that produce a gritty mouthfeel. These particles can also get stuck between the patients' teeth, producing a lingering grittiness and bitterness as further chewing breaks the coated particles. In pediatric formulations, the dose is generally small enough to allow flexibility with respect to the taste-masking approach. The physicochemical properties of an API also play an important role when selecting a taste-masking technology. For example, certain APIs have lower solubility at different pH values. Adding an alkalizing agent (such as sodium bicarbonate) or an acidifying agent (such as citric acid) can reduce solubility in the mouth, minimizing taste perception. You can also use a lower- solubility form of an API to reduce or eliminate poor taste. With a lower-solubility form of ranitidine base, the bitter taste can be adequately masked by flavors and sweeteners, but for more soluble forms of ranitidine (such as ranitidine hydrochloride), flavors and sweeteners may not be sufficient, particularly if the dosage form is an orally disintegrating tablet (ODT). Impact of substrate properties Processing and taste masking is more difficult for APIs with fine particles rather than coarse particles, and successful coating is easier when the particles have a narrow particle size distribution. The ideal particle shape for coating is a sphere; as sphericity increases, surface area decreases, producing more uniform coating. For taste-masked particles, the ideal size range is 100 to 400 microns, with an average (d50) particle size of approximately 200 to 300 microns. Excessive fines are prone to agglomeration during coating operations, which poses processing challenges and reduces yields, while