MICROBIAL STERILITY TESTING OF OIL-FORMULATED BOVINE SOMATOTROPIN USING TWEEN(R)-80 DISPERSION

The Food and Drug Administration requires that sterile pharmaceutical products be free of viable microorganisms. Sterility testing of pharma ceutical products provides added assurance that the product is sterile . Sterility testing is typically done by inoculating the drug product into microbial growth media followed by visual inspection for growth d uring incubation for a specified time period. A lack of visual growth indicates that the drug product samples tested were sterile. Formulate d Posilac(R) bovine somatotropin(1) consists of protein particles susp ended in an oil-based excipient. The product formulation is immiscible in aqueous media due to the excipient's water insolubility and the in solubility of the protein particles at near neutral pH values. Because the formulation is packaged and sold as a sterile product, it is crit ical that a sensitive microbial sterility test method be used for this key quality test. A sterility test method was developed for Posilac(R ) that utilized Tween(R) 80 (i.e. polysorbate 80) as a dispersant. Dis persion of the product using Tween(R) 80 produced a homogeneous suspen sion of bovine somatotropin particles and oil droplets in the micron s ize range. The suspension did not appreciably settle out with time, at testing to the homogeneous nature of the mixture. This method was foun d to be compatible with survival, recovery, and growth from low number s of the test organisms required by the U.S. Pharmacopeia XXIII as wel l as from two additional test cultures.