Pharmacokinetics and Pharmacodynamics (PK/PD) Studies

Pharmacokinetic / pharmacodynamics (PK/PD) modeling, an integral component of the drug development process, is a mathematical technique for predicting the effect and efficacy of drug dosing over time. Broadly speaking, pharmacokinetic models describe how the body reacts to a drug in terms of absorption, distribution, metabolism, and excretion. Pharmacodynamic models describe how a drug affects the body by linking the drug concentration to an efficacy (or safety) metric. A well-characterized PK/PD model is an important tool in guiding the design of future experiments and trials.

PK/PD Modeling Services

• • Development of PK/PD strategy as part of the drug development plan

• • Design of standalone Pharmacokinetic(PK) studies and sub-studies

• • Sample size and power calculations

• • Generation of randomization codes

• • Preparation of analysis plans

• • Compartmental and non-compartmental pharmacokinetic analysis

• •  Pharmacodynamic analysis

• • Assessment of PK/PD relationship

• • Assessment of Bioequivalence/Bioavailability

• • Drug interaction evaluations

• • Reporting

• • PK = Pharmacokinetics

– relationship between the dose administered and the changes in the drug concentration in the body with time. (Measured by drug concentration in blood, plasma, tissue)

– ADME

• » Absorption

• » Distribution

• » Metabolism

• » Elimination

• • PD = Pharmacodynamics

– relationship between drug concentration and its pharmacologic effect (Effects of a drug on the body / disease)

PK is a determinant of PD

Pharmacokinetics is the study of what the body does to the drug.Pharmacodynamics is the study of what the drug does to the body.

• • Pharmacodynamic Parameters

• • Dose-Response Relationships

• • Therapeutic Index

• • Dose–Response Relationship

  • » The numbers of receptors

  • » The willingness of a drug to associate with a receptor = receptor affinity

  • » The presence of other compounds competing for the binding site on the receptor = agonist /antagonist

  • » The concentration of the free drug in the vicinity of the receptor = pharmacokinetics

Therapeutic Index

The therapeutic index (also known as therapeutic ratio), is a comparison of the amount of a therapeutic agent that causes the therapeutic effect to the amount that causes death (in animal studies) or toxicity (in human studies).

PK-PD Changes in Critical Illness

• »  Circulatory Failure

• » Hepatic Failure

• » Renal Failure

• » Systemic Inflammatory Response Syndrome

• » Changes in Receptors in Acute Illness

• » Protein Binding

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