Development and Validation of Discriminatory In-vitro Release Method for Intramammary Drug Product.

Purpose: Intramammary (IMM) formulations are locally acting and delivered intracisternally into the udder. No pharmacopeial in-vitro release method is available to differentiate between the IMM formulations. Our research aim is to develop in-vitro release methods that discriminate different IMM formulations (SPECTRAMAST® LC and in-house formulations).

Methodology: Different in-house formulations were developed to simulate SPECTRAMAST® LC generics. SPECTRAMAST® LC and the in-house formulations were characterized for physicochemical attributes, such as particle size, rheology, drug content, sedimentation rate, and flocculation rate. The in-vitro release method was optimized by evaluating drug release using USP apparatuses 1, 2 (with and without enhancer/customized cells), and 4. Various test parameters, including medium effect (whole homogenized bovine milk versus aqueous buffer), medium volume (200-900 mL), and rotational speed (50-200 rpm) were investigated.

Results: Two potential in-vitro systems can be used as discriminatory methods for IMM formulations: USP apparatus 2 with the IMM formulation loaded into two containers a) customized formulation container (83.1 cm in height and 56.4 cm in width) or b) enhancer cells with their top adapted with mesh #40 (rotation speed:125 rpm and 900 mL of whole homogenized bovine milk). The release profile of SPECTRAMAST® LC at 1 h (99.8%) was not significantly different from formulations with similar physicochemical characteristics F-01 (99.1%) and F-02 (100.5%). Formulation with different physicochemical characteristics F-03 (44.3%) and F-04 (57.2%) showed slower release (1 h) than SPECTRAMAST® LC (98.8%).

Conclusion: The developed in-vitro release methods can be used as a potential tool for in-vitro comparability evaluations for IMM formulations.