Mathematics of Sterilization - Webinar CD/Transcript

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Mathematics of Sterilization

The FDA has been vocal about their commitment to stemming the outbreak of sterilization concerns, both on the drug and devices sides.  Headquarters and field personnel are cracking down - in the past six months seven compounders across the U.S. have gotten warning letters about sterilization.

Jerry Dalfors, the man the FDA asked to teach their own field inspectors about this topic, will discuss the definition of “sterile” and how to get there.

He’ll describe different sterilization methods, various approaches to be used for the validation of a sterilization process (using moist heat as template that can be applied to other methods) and what is required for routine monitoring and control of sterilization. 

Plus, he will review the causes for FDA warning letters for inappropriate sterilization development, validation and on-going assessment of the process.

This presentation will cover lethality, the different elements that affect D-value and Z-value, and how to calculate the probability and determine that you have essentially zero risk in your products due to a lack of sterility.

During this 90 minute presentation you will learn to demonstrate consistent validation to achieve a significant cost reduction with minimal patient risk, specifically:

  • How to use survivor curves, to determine D-values and Z-values
  • How linear regression can be used to calculate the edge of failure
  • How to use fraction-negative studies when multiple products or sites must be evaluated
  • Correction factors associated with heating and cooling
  • Cold spot determination
  • Calculation of process lethality
  • Which biological indicators to use, and how to make the selection
  • What laboratory studies are best for supporting sterilizer studies
  • The identification of elements in the process that can affect D-value


Different microorganisms in different environments during sterilization have different resistance to the destructive principles that cause the organism or spore to die. Some organisms have their optimal growth temperature at 110°C, whereas most vegetative cells are killed at 60°C. Some species are highly radiation resistant. The chemical environment causes significant variance in the death rate of a microorganism. Very dense cell walls, spore coats, or slime layers outside the cell can severely limit the effect of what is being used to sterilize the product.

Heat sterilization is a probability function dependent on heat exposure, the number of microorganisms, and the heat resistance of the microorganisms.

Current regulations expect the sterilization process to provide a level of assurance of at least 1x10-6 probability (fewer than one non-sterile unit per million units) of survival (non-sterility) for terminally sterilized parenteral drugs and medical devices. Since regulations require that you generate in your sterilization processes a probability of a non-sterile unit (PNSU), how do you use D-values, Z-values and F0 to calculate the probability and determine that you have essentially zero risk in your products due to a lack of sterility?

This course will be of benefit:

  • Manufacturing Operations
  • Technical Operations and Validation Professionals
  • Formulation
  • Engineering
  • QA/QC
  • Product and Process Development
  • Regulatory Affairs
  • Research and Development
  • Sterility Assurance

From the following companies:

  • All injectable drugs and biologics
  • Sterile devices and kits
  • Vaccines

Jerry Dalfors, Principal JD Technologies.
Mr. Jerry Dalfors has 40-plus years of business administration, consultative, technical and managerial experience in the development and manufacture of highly regulated biopharmaceutical products including injectables, biologics, medical devices and oral dosages. He has held permanent employee, temporary employee and company representative management positions with a multitude of the major pharmaceutical and biotechnology companies in the US. He has worked with or assisted more than two dozen companies with the establishment of controlled document/quality systems, FDA briefing and submittal documents, project management of several multi-million dollar projects including design, start-up and validation to assure fast track FDA approval by maintaining strict regulatory compliance during all phases of engineering, construction, commissioning and validation, and has written numerous submission documents for product, process and facility approval/licensing which also required the development of quality systems that included customer complaint management, deviation management, CAPA and associated site wide employee training. Each of his projects have been received and accepted by the FDA and other regulatory agencies. Jerry is considered an expert in almost all aspects of the biopharmaceutical and medical device industry, and has trained many FDA field inspectors. None of his work has ever received a 483, but he has corrected and prevented many, along with Warning Letter remediation.