The vacuum integrity of freeze dryers is critical for attaining adequate process control and maintaining confidence in sterility assurance which is key for the manufacture of sterile pharmaceutical products. Although discussions on the topic have been published, there is no industry standard established that is based on empirical data or that has a justifiable scientific rationale. This article provides a review of the scientific literature in the public domain and most importantly, a perspective from 14 Pharmaceutical companies on the leak rate specifications commonly used in industry. Using this information we recommend a best practice for the lyophilizer leak rate test which includes detailing necessary preparation activities following Steam-In-Place (SIP) sterilization, defining a period of stabilization to eliminate pressure and temperature fluctuations and details of the test conditions and the test period.

We conclude that for routine manufacturing practice the operational leak rate should not exceed 20 µbar L/s and we provide additional guidance for large volume and older lyophilisation equipment.

Orla McGarvey, Ph.D, Associate Director, Process Development, DPS

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