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# The Difference Between Vd and Vss

There are many terms used to represent volume of distribution, but two common ones are Vd and Vss. Vd is the apparent volume of distribution. It can be calculated using the following equation:

$Vd=\frac{F*D}{AUC_{0-t}*k_{el}}$

Vss is the apparent volume of distribution at steady state. Or, the sum of all volume terms in a multicompartment model. It can be calculated using the following equation:

$Vss=\frac{D*AUMC_{infty}}{AUC_{infty}^2}$

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### 筆者について

By: Nathan Teuscher
Dr. Teuscher has been involved in clinical pharmacology and pharmacometrics work since 2002. He holds a PhD in Pharmaceutical Sciences from the University of Michigan and has held leadership roles at biotechnology companies, contract research organizations, and mid-sized pharmaceutical companies. Prior to joining Certara, Dr. Teuscher was an active consultant for companies and authored the Learn PKPD blog for many years. At Certara, Dr. Teuscher developed the software training department, led the software development of Phoenix, and now works as a pharmacometrics consultant. He specializes in developing fit-for-purpose models to support drug development efforts at all stages of clinical development. He has worked in multiple therapeutic areas including immunology, oncology, metabolic disorders, neurology, pulmonary, and more. Dr. Teuscher is passionate about helping scientists leverage data to aid in establishing the safety and efficacy of therapeutics.

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