Pharmacokinetics and Pharmacodynamics

As an advanced practice nurse assisting physicians in the diagnosis and treatment of disorders, it is important to not only understand the impact of disorders on the body, but also the impact of drug treatments on the body. The relationships between drugs and the body can be described by pharmacokinetics and pharmacodynamics.

Pharmacokinetics describes what the body does to the drug through absorption, distribution, metabolism, and excretion, whereas pharmacodynamics describes what the drug does to the body.

hen selecting drugs and determining dosages for patients, it is essential to consider individual patient factors that might impact the patient’s pharmacokinetic and pharmacodynamic processes. These patient factors include genetics, gender, ethnicity, age, behavior (i.e., diet, nutrition, smoking, alcohol, illicit drug abuse), and/or pathophysiological changes due to disease. Pharmacokinetics and Pharmacodynamics

For this Discussion, you reflect on a case from your past clinical experiences and consider how a patient’s pharmacokinetic and pharmacodynamic processes may alter his or her response to a drug.

To Prepare

• Review the Resources for this module and consider the principles of pharmacokinetics and pharmacodynamics.
• Reflect on your experiences, observations, and/or clinical practices from the last 5 years and think about how pharmacokinetic and pharmacodynamic factors altered his or her anticipated response to a drug.
• Consider factors that might have influenced the patient’s pharmacokinetic and pharmacodynamic processes, such as genetics (including pharmacogenetics), gender, ethnicity, age, behavior, and/or possible pathophysiological changes due to disease.
• Think about a personalized plan of care based on these influencing factors and patient history in your case study. Pharmacokinetics and Pharmacodynamics

Post a description of the patient case from your experiences, observations, and/or clinical practice from the last 5 years. Then, describe factors that might have influenced pharmacokinetic and pharmacodynamic processes of the patient you identified. Finally, explain details of the personalized plan of care that you would develop based on influencing factors and patient history in your case. Be specific and provide examples.

Rubric:

Answers all parts of the discussion question(s) expectations with reflective critical analysis and synthesis of knowledge gained from the course readings for the module and current credible sources.

Supported by at least three current, credible sources.

Written clearly and concisely with no grammatical or spelling errors and fully adheres to current APA manual writing rules and style. Pharmacokinetics and Pharmacodynamics

References:

Rosenthal, L. D., & Burchum, J. R. (2018). Lehne’s pharmacotherapeutics for advanced practice providers. St. Louis, MO: Elsevier.

• Chapter 1, “Prescriptive Authority” (pp. 1–3)
• Chapter 2, “Rational Drug Selection and Prescription Writing” (pp. 5–9)
• Chapter 3, “Promoting Positive Outcomes of Drug Therapy” (pp. 11–16)
• Chapter 4, “Pharmacokinetics, Pharmacodynamics, and Drug Interactions” (pp. 17–40)
• Chapter 5, “Adverse Drug Reactions and Medical Errors” (pp. 41–49)
• Chapter 6, “Individual Variation in Drug Response” (pp. 51–56)
  

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Clinical pharmacology is the study of the interactions between drugs and the human body. Pharmacokinetics and pharmacodynamics are two broad divisions within clinical pharmacology. The complex, biochemical interactions that occur between the body’s natural processes and the chemical composition of a pharmaceutical drug are measured and described by pharmacokinetics and pharmacodynamics which both play a pivotal role in determining a drug’s safety and efficacy. Pharmacokinetics and Pharmacodynamics

Regulatory agencies, such as the FDA, are responsible for approving new drugs or deciding whether or not a drug should be taken off the market. Regulatory agencies are also responsible for ensuring that all available drugs are effective and safe for human use. Understanding the safety and effectiveness of any drug depends, in part, on pharmacokinetics and pharmacodynamics.

Pharmacokinetics vs. Pharmacodynamics

The main difference between pharmacokinetics and pharmacodynamics is that pharmacokinetics (PK) is defined as the movement of drugs through the body, whereas pharmacodynamics (PD) is defined as the body’s biological response to drugs. In other words, PK describes a drug’s absorption, distribution, metabolism, and excretion (also known as ADME) and PD describes how biological processes in the body respond to or are impacted by a drug. Put in the simplest terms, pharmacokinetics is what the body does to the drug and pharmacodynamics is what the drug does to the body.

While PK describes a drug’s exposure by characterizing its ADME properties and bioavailability as a function of time, PD describes a drug’s response in terms of biochemical or molecular interactions. PK/PD together can be thought of as an exposure/response relationship. Pharmacokinetics and Pharmacodynamics

Understanding the exposure-response relationship (PK/PD) is key to the development and approval of every drug. PK and PD data contribute to about 25% of what is in a drug package insert or drug label. Strategic planning of the overall drug development program and an intelligent pharmacokinetic study design can accelerate the development process to help ensure safety and efficacy endpoints are achievable.

The Importance of Pharmacokinetic and Pharmacodynamic Analyses

PK and PD analyses are important because they help us understand how drugs behave in the body and how the body reacts to drugs, respectively. Drug developers use insights gained from PK and PD analyses to design better clinical studies (i.e., what dose to use or how different drugs interact with each other in the body). Clinicians use the information from PK and PD analyses (as presented in the drug label or package insert) to treat different types of patients (e.g., patients with and without renal impairment or elderly versus younger patients). Pharmacokinetics and Pharmacodynamics

How to Use Pharmacokinetic and Pharmacodynamic Analyses

PK and PD analyses can be used to determine a number of important drug development parameters related to clinical study design. PK and PD analyses can be used to:

• Characterize drug exposure: With the exception of drugs delivered intravenously, only a fraction of a drug’s dose is absorbed and pharmacologically active. Quantifying the rate and magnitude of exposure to a drug is critical for determining how best to guide its use in the clinic.
• Determine an appropriate dose for a clinical study: PK and PK/PD modeling can help predict dosing requirements early in the development process (i.e., dose justification), making the first dose-range finding studies informative and consequential.
• Assess changes in dose requirements: Assessing and predicting the effect of dosing changes is important early in the development process to provide insights into designing better clinical studies.
• Estimate the rate of elimination and absorption: Knowing how quickly a drug is absorbed and eliminated can help make decisions regarding formulation design and dosing regimens.
• Assess relative bioavailability/bioequivalence: Comparing the extent of a new formulation’s absorption to an existing formulation can often help demonstrate therapeutic advantages. Pharmacokinetics and Pharmacodynamics
• Characterize intra- and inter-subject variability: High variability can quickly derail clinical development programs. Understanding how a drug’s PK and PD change within and between individuals can help design clinical trials in ways that reduce variability and make the results more robust.
• Understand concentration-effect relationships: The concentration-effect relationship is the cornerstone of pharmacodynamics. Identifying the variables that affect this relationship is critical for a successful development program.
• Establish safety margins and efficacy characteristics: Successful drugs have clearly defined therapeutic windows. PK/PD modeling can help determine dosing thresholds. Sola dosis facit venenum… “The dose makes the poison” Pharmacokinetics and Pharmacodynamics
  

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