PK/PD Modeling & Simulation

The difference between Vd and Vss

Nathan Teuscher

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: Vss is the apparent volume of distribution at steady state. Or, the sum of all volume terms in a multicompartment model. It […]

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Topics: PK/PD Modeling & Simulation

What is Shrinkage?

Nathan Teuscher

In 2007, Mats Karlsson and Radojka Savic published a perspective in Clinical Pharmacology & Therapeutics titled “Diagnosing Model Diagnostics” (link to CP&T website). In this article they examined the use of diagnostic plots to evaluate the adequacy of model fits for nonlinear mixed-effects analysis. Although there is a wealth of information in this article, the […]

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Topics: PK/PD Modeling & Simulation

Is a Monte Carlo Simulation an Exotic Drink?

Nathan Teuscher

The term “Monte Carlo simulation” is often used in the modeling and simulation literature with PK/PD analysis. When I was first exposed to this term, I was thoroughly confused and thought that it was some exotic statistical method that required 3 PhDs and a few days to comprehend. Well, I was very wrong. A Monte […]

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Topics: PK/PD Modeling & Simulation

What is WinNonlin?

Nathan Teuscher

A reader suggested that I write a similar post about WinNonlin. Great idea! Thank you! WinNonlin is a pharmacokinetic software package that has grown and evolved over the past 20 years. The most familiar versions of WinNonlin (v3 – v5) were stand-alone Windows-based software packages used to perform non-compartmental analysis and single subject non-linear model […]

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Topics: PK/PD Modeling & Simulation

What is the Difference Between Individual and Population PK?

Nathan Teuscher

Pharmacokinetic analysis is often broken into two areas … “PK” and “population PK”. Sometimes the first term “PK” is also called “individual PK”. I’d like to demystify these two analysis methods in this post. In the analysis of biological samples, we have many different detection technologies, for example mass spectroscopy, UV spectroscopy, radiometric detection, and […]

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Topics: PK/PD Modeling & Simulation

Software Validation: Do I Have to Do It?

Nathan Teuscher

The topic of software validation in pharmacokinetics is one of great debate now, and has been for many years. This debate often ends with absolutes like “you have to validate” or “there is no need to validate” the PK software being used. Software validation became a “hot” topic in the pharmacokinetic realm when the FDA […]

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Topics: PK/PD Modeling & Simulation
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