First Order and Zero Order Kinetics Quiz and Flashcards

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Questions and Answers

What is a characteristic of drugs that demonstrate first-order kinetics?

The concentration of the drug in the blood will decrease in a linear fashion over time.

The half-life of elimination is constant regardless of the amount of drug in the body. (correct)

The elimination mechanisms are saturated at concentrations of clinical interest.

The rate of elimination is constant regardless of concentration.

What is the term for the rate of elimination that is constant regardless of concentration?

Zero-order elimination (correct)

Non-linear elimination

First-order elimination

Linear elimination

What is the typical pattern of concentration decrease for drugs that demonstrate zero-order elimination?

The concentration decreases in a linear fashion over time. (correct)

The concentration decreases by 50% for every half-life.

The concentration remains constant over time.

The concentration decreases in a logarithmic fashion over time.

What is the purpose of a two-compartment model in pharmacokinetics?

To simulate the behavior of a drug that undergoes an early distribution phase followed by a slower elimination phase. Signup and view all the answers

What is a characteristic of the elimination phase of a first-order drug when plotted on a logarithmic axis?

It is a straight line. Signup and view all the answers

What is the term for the time it takes for the concentration of a drug to decrease by 50%?

Half-life Signup and view all the answers

What is the characteristic of drugs with first-order kinetics?

The rate of elimination is proportional to concentration. Signup and view all the answers

What is the characteristic of zero-order elimination?

The rate of elimination is constant and independent of concentration Signup and view all the answers

What is the initial curvilinear portion of the serum concentration-time curve representing?

Distribution phase Signup and view all the answers

What is the primary function of the Food and Drug Administration (FDA) in the United States?

To regulate the sale and use of drugs. Signup and view all the answers

How is the elimination half-life typically measured?

By measuring the time between any two plasma concentration points on the elimination phase that differ by twofold Signup and view all the answers

What type of elimination is characterized by a constant rate of elimination, regardless of concentration?

Zero-order elimination Signup and view all the answers

What is the goal of rational molecular design or screening?

To find a molecule that selectively alters the function of the target Signup and view all the answers

What is a prerequisite for a new drug to be approved for regular therapeutic use in humans?

A series of animal and experimental human studies. Signup and view all the answers

What is the characteristic of 'me-too' drugs?

They are the result of simple chemical alteration of the pharmacokinetic properties of the original prototype agent Signup and view all the answers

What is the purpose of constructing accurate mathematical models in pharmacokinetics?

To predict the behavior of drugs in the body. Signup and view all the answers

What is the significance of a drug being distributed to only one compartment?

It behaves as if it were restricted to the vascular compartment. Signup and view all the answers

What is the significance of the linear portion of the serum concentration-time curve?

It represents the elimination phase of the drug Signup and view all the answers

Study Notes

Drug Elimination

Drugs with first-order elimination have a constant half-life of elimination, regardless of the amount of drug in the body.
The concentration of a first-order elimination drug in the blood decreases by 50% for every half-life.
Most drugs in clinical use demonstrate first-order kinetics.
Zero-order elimination involves a constant rate of elimination, regardless of concentration.
Zero-order elimination drugs do not have a constant half-life, and their concentrations in plasma decrease in a linear fashion over time.

Pharmacokinetic Models

A two-compartment model is used to simulate the distribution and elimination phases of a drug.
The two compartments consist of the blood and the extravascular tissues.
Each phase has a characteristic half-life: 1/2a for the first phase, and 1/2β for the second phase.
When concentration is plotted on a logarithmic axis, the elimination phase for a first-order drug is a straight line.

Distribution Models

Some drugs behave as if they were distributed to only 1 compartment (e.g., if they are restricted to the vascular compartment).
Others have more complex distributions that require more than 2 compartments for accurate mathematical models.

Drug Development and Regulation

The sale and use of drugs are regulated in almost all countries by governmental agencies, such as the FDA in the United States.
New drugs are developed in industrial or academic laboratories, and must undergo a series of animal and experimental human studies (clinical trials) before being approved for therapeutic use.
New drugs can emerge from a variety of sources, including the identification of a new target for a disease.

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Description

Understand the concepts of first-order and zero-order elimination in pharmacokinetics, including their characteristics and effects on drug concentration in the body.

Pharmacokinetics: First-Order and Zero-Order Elimination

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