Mastering Polymorphism: How Neusilin® US2 Stabilizes Bilastine For Optimized Formulations

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THE POLYMORPHISM CHALLENGE IN BILASTINE FORMULATION

Bilastine is a second-generation, non-sedating H1-antihistamine widely used for treating allergic rhino-conjunctivitis and urticaria. However, its formulation presents significant pharmaceutical hurdles due to its complex polymorphic behavior.

Bilastine exists in multiple crystalline forms, and exposure to humidity and temperature can trigger conversion to less desirable hydrates or polymorphic impurities, with potential impact on dissolution and bioavailability. From a formulator’s standpoint, controlling solid-state form is therefore as important as meeting conventional critical quality attributes QAs such as hardness, friability, and disintegration.

ROLE OF NEUSILIN® US2 IN BILASTINE

The patent EP3470062A1 and WO 2017/017301 demonstrates that magnesium aluminometasilicate (Neusilin®, specifically Neusilin® US2) has an unexpected stabilizing effect on Bilastine, particularly when the API is present as polymorphic form 2 or 3. In the compositions mentioned in the patent, Neusilin® prevents transformation to Bilastine hydrates that are otherwise seen under stress and eal-time conditions, thus stabilizing the desired crystalline form over shelf life. Mechanistically, Neusilin® a porous, amorphous magnesium aluminometasilicate can:

Importantly, Neusilin® also functions as a glidant, improving powder flowability of the Bilastine blend prior to compression without compromising dissolution, which is maintained via the presence of a watersoluble filler. This synergy – polymorphic stabilization plus better flow and unchanged rapid dissolution is highlighted as a key inventive step in the patent.

OPTIMIZED BILASTINE – NEUSILIN® TABLET FORMULA

The patent discloses Bilastine tablets in which Neusilin® US2 is an integral structural excipient in the final optimized formulation. A representative optimized composition (per tablet) is as follows:

The key design element is the co‑presence of:

Crystalline Bilastine (polymorph 2 or 3)
Neusilin® US2 at a level sufficient to stabilize the crystalline form and ensure good flow.

A water‑soluble filler that preserves or enhances bilastine dissolution, which is not negatively impacted by Neusilin®.

Continue reading and see the full Pharmaceutical Technical Newsletter on Mastering Polymorphism here:

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