Scale-Up of Dispersed Parenteral Dosage Forms 407 (B) Fig. 7 Continued. PRODUCT PRODUCT Fig. 8 Principle of a hydroshear homogenizer.

Scaling up of sterile filtration is often dictated by the configuration of filters available from manufacturers. These days, all leading manufacturers provide filters that range in surface area over factors of 100 or more. While scaling up sterile filtration it generally is desirable to maintain the same bulk flow velocity through the filters. Often this can be achieved only by assembling a filtration battery with multiple filters in parallel. Such batteries can be tricky to operate, as fluids tend to take paths of least resistance, which can result in some of the parallel filters not getting any product. Judicious use of valves to throttle the flow is necessary. In today's regulatory climate, media runs are required to validate any aseptic process. (In media runs, a growth medium like tryptic soy broth is used to simulate the process.) During such media runs, a filtration battery with the maximum number of parallel filters that will ever be used simulate the worstcase scenario.