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excipients Tablets & Capsules April 2018 39 on eye Oliver Luhn and Joerg Bernard Suedzucker Michael Black and Maj-Britt Cepok Beneo-Palatinit In this edition of Eye on Excipients, researchers present the results of a study that examined how isomalt can be used as a carrier for liquid APIs in solid oral dosage forms. M a n y a c t i v e p h a r m a c e u t i c a l ingredients (APIs) can be formulated into either liquid or solid oral dosage forms. A major advantage of liquid dosage forms is that the API is already dissolved and generally absorbs more quickly in vivo. Solid dosage forms, on the other hand, have the advantage of not requiring preservatives and are generally more stable and easier to handle. A liquisolid is a tablet or powder with a liquid API absorbed into a solid carrier excipient in an effort to combine the advantages of both liquid and solid dosage forms. Companies have successfully formulated liquisolids to enhance the bioavailability of poorly soluble APIs such as carbamazepine [1], fenofibrate [2], and hydrochlorothiazide [3]. To create the liquisolid, the API is dissolved or suspended in a suitable non-volatile liquid and then blended with porous excipients to create a free- flowing, compactable dry powder [4]. The resulting liquisolid system has an enhanced dissolution profile due to the increased surface area, increased aqueous solubility, and improved wettability compared to a dry formulation of the same API. However, formulating a liquisolid system presents certain challenges. Compared to the solid carrier, the liquid is virtually non-compressible, so the carrier must be able to absorb a sufficient amount of the liquid while retaining compactability and flowability. In addition, the liquid absorption must be strong enough to prevent leaking during tableting or stability testing but not so strong as to prevent adequate dissolution. Companies frequently use dibasic calcium phosphates, magnesium aluminometasilicates, and silicon dioxides to convert liquid APIs into free-flowing powders because the porous structure of these excipients provides a large specific surface area Table 1 Materials Material Dynamic viscosity (cP) Supplier Linseed oil 30 Mühle Schlingemann Simethicone Q7-2243 LVA 440 Dow Corning Simethicone antifoam C100EP 2,450 KCC Europe galenIQ 721 (Isomalt EP, USP-NF, JP) NA Beneo-Palatinit Figure 1 Crystal shapes of isomalt constituents a. GPS crystal b. GPM crystal

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