Lecture 2 Flashcards
Why use PK models?
Predictive Tool
PK models offer ________________ of complex body processes, providing a framework to predict a drug’s behavior within the body
simplifcations
Why use PK models?
A PK model acts as a hypothesis, utilizing mathematical expressions to concisely describe and establish quantitative relationships btwn various factors affecting drug factors
Why use compartmental models?
_________________:Compartmental models apply mathematical principles to various physiological processes, creating a simplified representation.
_______________:The effectiveness of a model in predicting drug behavior is rooted in the accurate choice of mathematical functions that capture the key factors driving the kinetic process.
Types of Models:The basic types of compartmental models are differentiated by the number of compartments required to depict a drug’s behavior accurately.
Simplification
Predictive capability
What is a ____________?
It’s not an actual physiological or anatomical region. Instead, it represents a tissue or group of tissues with comparable blood flow and drug affinity
Compartment
Notion of ‘Compartment’:
Think of a compartment as a “kinetic space,” a conceptual tool rather than a physical location
Highly Perfused Organs:
Organs like the __________, liver, kidneys, and lungs are grouped into one compartment due to their analogous drug distribution patterns.
heart
______________ Compartment:
This compartment consists of plasma and highly blood-perfused organs. These organs and tissues rapidly equilibrate with the drug, making them central to its distribution.
Central
____________-Compartment:
This compartment includes fat tissue, muscle, cerebrospinal fluid (CSF), and other less perfused areas.
Peripheral
Determining Model Type:
Observed drug concentrations in the body guide the selection of the appropriate compartmental model to accurately describe the drug’s pharmacokinetics
Compartmental Pharmacokinetics Models
The value of a model is determined by how well it predicts ____________in fluids and tissues
Generally it is best to use the simplest model that accurately predicts changes in organ
drug concentration
Pharmacokinetics Models
Uses of Pharmacokinetic Models:
____________Predictions:Foresee drug concentrations in plasma, tissues, and urine for any given dose or administration route.
__________ Estimates: Predict potential accumulation of drugs and their metabolites.
Concentration and Activity Correlation: Relate drug concentrations to their pharmacological effects.
Impact of Physiological Changes:Understand how alterations in physiology or the presence of disease influence drug absorption,distribution, or elimination.
Drug Level
Accumlation
Pharmacokinetic models can be used to:
(i) Predict plasma, tissue, and urine drug
levels with any dose at any time
(ii) Predict the effect of the drug over
time
(iii) Calculate suitable dosage regimen
(iv) Estimate the rate of ADME processes
Answer:i & iii & iv
Highly perfused organs and blood comprise what is usually known as the peripheral compartment.
False
A compartment is an anatomic region which has a tissue or group of tissues with similar blood flow and drug affinity
False
Assumption: FirstOrder Kinetics
Definition:
– In _________________ kinetics, the elimination rate or change in drug concentration is directly proportional to the amount of drug present in the body.
2. Mathematical Representation:
Rate = k * [Drug Concentration]
Where “k” is the first-order rate constant.
- Graphical Representation:When plotted on a semilogarithmic graph, first-order kinetics
produce a ____________line, highlighting its constant proportionality. - Clinical Implications: A majority of drugs in therapeutic settings follow first-order kinetics, making it easier to predict plasma drug concentrations over time and adjust dosing regimens accordingly.
first-order
straight line
Apparent Volume of Distribution (Vd)
_________quantifies the distribution of a drug throughout the body
It represents the volume wherein the drug appears to be dispersed.
Vd
Vd gives an idea of the space a drug seems to occupy within the body.
- Vd is derived from the drug dose (or injected amount) and
the drug concentration in the plasma right after the
injection, denoted as Cp0.
When both the elimination rate constant (kel) and clearance
(CL) are available, Vd can be calculated using:V=CL/kel
Apparent volume of distribution
Assumption: The drug distributes _________ and ________ throughout the Assumption apparent volume.
rapidly and uniformly
_________________:Represents the volume in which a drug appears to be evenly distributed when it reaches equilibrium
apparent volume of distribution
Conc = ______ /_________
Mass/volume
𝐕𝐨𝐥𝐮𝐦𝐞 𝐨𝐟 𝐃𝐢𝐬𝐭𝐫𝐢𝐛𝐮𝐭𝐢𝐨𝐧=Amount of Drug in the Body/Plasma drug concentration
Apparent volume of distribution
It is not a physical or physiological volume
Instead, it mirrors the space the drug seems to occupy within the body
Apparent volume of distribution
Acts as the proportionality term between the drug’s mass and its concentration.
Imagine the volume of water required to achieve the same drug concentration as observed in the blood.
Example: If 3 g of a drug is added and
distributed throughout a tank and the resulting
concentration is 0.15 mg/mL, how much is the
volume of the tank?
