Pharmacokinetics Quiz

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Questions and Answers

Which of the following best describes the process of drug absorption?

The transfer of a drug from the administration site into the bloodstream. (correct)

The passage of drugs into various body fluid compartments.

The removal of the drug from the body.

The changing of a drug by the body to assist with excretion.

What is the primary site of drug metabolism in the body?

Liver (correct)

Lungs

Kidney

Brain

Which of the following is a factor that influences the rate of drug absorption?

Organ size

Drug excretion rate

Blood flow at injection site (correct)

Plasma protein binding capacity

What is the process by which drugs are transported to various body fluid compartments?

Distribution (A) Signup and view all the answers

Which of these is NOT a factor that determines the distribution of a drug?

Route of administration (C) Signup and view all the answers

What is the purpose of drug metabolism (biotransformation)?

To make the drug easier to excrete (A) Signup and view all the answers

Which of the following is an example of a drug being metabolized from an inactive to active form?

acyclovir (B) Signup and view all the answers

What does the process of drug excretion accomplish?

It terminates the drug's effects (D) Signup and view all the answers

What is the primary function of the kidneys in the context of pharmacokinetics?

Excreting drugs and their metabolites from the body. (A) Signup and view all the answers

If a drug has a half-life of 2 hours, approximately how long will it take for the drug to be considered eliminated from the body?

8 to 10 hours (C) Signup and view all the answers

A drug’s half-life is defined as:

The time it takes for the concentration of the drug to fall to half its original level. (D) Signup and view all the answers

Which of the following is an example of a drug that follows zero-order kinetics?

Aspirin (D) Signup and view all the answers

What does the term 'onset' refer to in the context of drug administration?

The time it takes for the drug to have a therapeutic effect. (D) Signup and view all the answers

Which of the following is NOT considered a parenteral route of drug administration?

Oral administration (C) Signup and view all the answers

What does a dose-response curve demonstrate?

The relationship between the administered dose of a drug and the resulting effect. (A) Signup and view all the answers

Which of the following is considered an enteral route of drug administration?

Rectal administration (A) Signup and view all the answers

Which of these factors does NOT directly alter a drug's effects in the body?

Patient’s diet (A) Signup and view all the answers

What is a key feature of the therapeutic range on a log dose-effect curve?

The curve shows a sharp increase in effect, corresponding to a rapid rise in response. (A) Signup and view all the answers

What is the maximum response of a drug on a log dose-effect curve?

The point where the curve plateaus, showing the greatest response a drug can achieve. (B) Signup and view all the answers

How is drug potency defined?

The amount of drug required to achieve a particular effect. (A) Signup and view all the answers

If a drug has a higher potency, what does that indicate about the dose needed for an effect?

A smaller dose is needed. (D) Signup and view all the answers

Which curve model is more complex and represents the relationship between the actual dose of the drug and the actual response?

Log dose-effect curve model. (A) Signup and view all the answers

What is the relationship between a drug's potency and the dose required to produce a certain pharmacological effect?

Higher potency means lower dose is required. (B) Signup and view all the answers

What does the 'pinch your ear harder' analogy illustrate about the dose-response curve?

The relationship between increasing dose and increasing effect. (A) Signup and view all the answers

What does the term 'efficacy' of a drug refer to?

The maximum response a drug can produce. (C) Signup and view all the answers

A drug has a median lethal dose (LD50) of 500 mg/kg and a median effective dose (ED50) of 25 mg/kg. What is its therapeutic index (TI)?

20 (B) Signup and view all the answers

Which of the following statements best describes a drug with a high therapeutic index?

It is likely to produce therapeutic effects with minimal adverse reactions. (C) Signup and view all the answers

Why can't a drug create a new function in an organism?

Drugs exploit existing pathways by mimicking or blocking endogenous agents. (D) Signup and view all the answers

What distinguishes a drug agonist from an antagonist?

Agonists bind to a receptor and produce an effect, while antagonists counteract the agonist's action. (D) Signup and view all the answers

Which of the following statements is true regarding a drug with a high affinity for its receptor?

Less of the drug is required for the same effect, and more receptors are occupied. (B) Signup and view all the answers

What is the study of pharmacokinetics primarily concerned with?

How the body affects a drug (absorption, distribution, metabolism, excretion). (D) Signup and view all the answers

A drug produces nausea and vomiting as an undesirable consequence. What type of effect is this considered?

Adverse effect (B) Signup and view all the answers

Which route of drug administration is characterized by a slower onset of action and is considered the safest, least expensive, and most convenient?

Oral (D) Signup and view all the answers

What is the primary disadvantage associated with using the intravenous route of drug administration?

Risk of phlebitis and rapid onset side effects. (C) Signup and view all the answers

A patient is experiencing severe vomiting and requires medication. Which route of administration would be most suitable?

Rectal (A) Signup and view all the answers

What is a significant disadvantage of the rectal route of drug administration?

Poor patient acceptance & irregular drug absorption (A) Signup and view all the answers

What advantage does the intramuscular route have over the subcutaneous route for certain medications?

Allows increased tolerance to irritating drugs and suspensions (D) Signup and view all the answers

A drug is rapidly metabolized by the liver when it first enters circulation. Which route of administration is most likely affected by this 'first pass' effect?

Oral (D) Signup and view all the answers

Why is the intravenous route generally used in emergency situations?

It produces the most rapid drug response (A) Signup and view all the answers

Which of these routes involves injecting a drug directly into the spinal space?

Intrathecal (D) Signup and view all the answers

What is a key advantage of administering drugs through inhalation?

Rapid onset of action (A) Signup and view all the answers

A patient presents with a large area of abraded skin, if topical anesthetic is applied, what is a primary risk to consider?

Elevated risk of systemic side effects (D) Signup and view all the answers

Which route of drug administration is most effective in non-keratinized areas?

Topical (B) Signup and view all the answers

What is a disadvantage associated with the inhalation route of drug administration?

Potential for abuse (D) Signup and view all the answers

Which of the following topical applications involves a drug applied directly onto the skin?

Epicutaneous (A) Signup and view all the answers

Study Notes

Drug Action and Handling

Drug action and handling is covered in Chapter 2.

Characterization of Drug Action

Drug response or action is measured using terms like dose-response curves, log dose-effect curves, potency, and efficacy.

Dose-Response Curve

A simple model where increasing the dose increases the response (e.g., pinching your ear harder hurts more).
The intensity of the response increases proportionally with the dose.

Log Dose Effect Curve

A more complex model showing the relationship between the drug dose and the resulting response.
The curve shows a gradual increase in response as the log dose increases.
The curve plateaus at the maximum response which is the ceiling effect.

Therapeutic Range & Maximum Response

Therapeutic range: the dose range where the response increases sharply; the desired dose is in this zone.
Maximum response: the point on the curve showing the highest response possible from administering more of the drug.

Potency

Potency is the amount of drug needed to produce an effect.
Higher potency means a smaller dose is needed for the same response.
Drug A is more potent than Drug B if it produces an effect with a lower dose.

Efficacy

Efficacy is the maximum response a drug can produce, regardless of dose.
Increasing the dose does not increase efficacy; if the maximum response is reached, increasing the dose has no further effect.
Increasing a drug does not increase efficacy—it just increases the probability of side effects.

Therapeutic Index

TI (Therapeutic Index) is the ratio of the median lethal dose (LD50) to the median effective dose (ED50).
A higher TI indicates a safer drug.
A TI close to 0 suggests careful monitoring of the drug's administration is necessary.

TI Examples

Drug A: LD = 200mg, ED = 20mg, TI = 10
Drug B: LD = 300mg, ED = 100mg, TI = 3

Mechanism of Action of Drugs

Drugs do not create new functions.
They produce the same action as endogenous agents.
Drugs can replace or block the action of endogenous agents.
Drugs bind to the receptor site on the cell's membrane to have a desirable effect.
Adverse effects result from unintended drug actions on non-target organs.

Agonists and Antagonists

Agonists have affinity for a receptor, bind to it, and produce an effect.
Antagonists counteract the action of agonists by binding to receptors.
Drugs with stronger affinity bind to more receptors and are more potent.
More potent drugs will require a smaller dose to produce the same effect.

Pharmacokinetics ADME

Pharmacokinetics is the study of how a drug enters, circulates in, and is removed from the body.
Absorption, distribution, metabolism, and excretion are the key processes.

Pharmacokinetics: Drug Absorption

Absorption is the transfer of a drug from the administration site to the bloodstream.
Physicochemical properties, site of absorption, drug solubility, dose form, and blood flow at site of injection influence absorption rate.
IV (intravenous) administration bypasses this step

Pharmacokinetics: Drug Distribution

Distribution is the passage of drugs into various body fluid compartments (plasma, interstitial fluids, intracellular fluids).
Drugs distribute to organs with higher blood flow.
Factors affecting distribution include organ size, blood flow to organs, drug solubility, plasma protein-binding, and barriers like the blood-brain barrier and placenta.

Pharmacokinetics: Drug Metabolism

Metabolism, also called biotransformation, is the body's way of changing a drug molecule to excrete it more easily.
The liver is the primary site of metabolism.
Metabolism mechanisms include converting active drugs to inactive forms, inactive drugs to active forms, and active to active forms.
Impaired liver function and other substances can affect drug metabolism.

Pharmacokinetics: Drug Excretion

Excretion is the removal of drugs from the body through various pathways (renal, lungs, saliva, bile, gastrointestinal tract, sweat, milk).
Drug elimination ends the effects of the drug.

Clinical Pharmacokinetics: Half-Life

Drug half-life is the time it takes for the drug concentration to decrease by half.
4-5 half-lives are needed for a drug to be largely eliminated.
This is important for determining dosing schedules.
Example: Azithromycin (Zithromax) half-life is approximately 68 hours.

Half-Life First-Order Kinetics

Drug elimination in first-order kinetics is proportionate to the drug's plasma concentration.
The drug's concentration decreases by a constant percentage over a given time.

Half-Life Zero-Order Kinetics

In zero-order kinetics, drug elimination is constant for a given time period, regardless of drug concentration.
This occurs because elimination mechanisms are saturated; they can't keep up with a large dose.
Aspirin and alcohol have zero-order kinetics in some conditions.

Altering Drug Effects

Patient adherence, psychological factors, pathologic state, time of administration, route of administration, gender, genetic variation, drug interactions, age and weight, environment, and other factors can alter drug effects.

Routes of Administration

Onset: The time it takes for a drug to start having an effect.
Duration: The length of time a drug's effect lasts.
Enteral routes place drugs directly into the gastrointestinal tract (e.g., oral, rectal).
Parenteral routes bypass the gastrointestinal tract (e.g., intravenous, intramuscular, subcutaneous).

Oral Route of Drug Administration

Advantages: large absorbing area in the small intestine, slower onset of action, safest, least expensive, most convenient.
Disadvantages: nausea, vomiting, drug inactivation by GI tract acidity or enzymes, drug interactions, requires patient cooperation, first-pass effect (drug metabolized when first passing through the liver).

Rectal Route of Drug Administration

Advantages: used if patient is vomiting or unconscious, produces local or systemic effects.
Disadvantages: drugs are poorly and irregularly absorbed, poor patient acceptance.

Intravenous Route of Drug Administration

Advantages: most rapid drug response, more predictable blood levels, can be used in emergencies.
Disadvantages: phlebitis (inflammation of a vein), drug irretrievability, allergy, side effects related to high plasma concentrations.

Intramuscular Route of Drug Administration

Advantages: increased tolerance for irritating drugs, can administer suspensions resulting in a sustained effect.
Disadvantage is not listed.

Subcutaneous Route of Drug Administration

Method of injecting drugs into the subcutaneous areolar tissue.
Insulin and local anesthetics are often administered this way.
Disadvantages: irritating solutions may cause sterile abscesses or hematomas.

Other Routes of Drug Administration

Intradermal: Injection into the epidermis (e.g., tuberculin test).
Intrathecal: Injection into the spinal space.
Intraperitoneal: Injection into the body cavity.

Inhalation Route of Drug Administration

Examples: asthma inhalers, general anesthetics, nitrous oxide/oxygen.
Advantages: rapid onset of action, avoids needles.
Disadvantages: often leads to drug abuse.

Topical Route of Drug Administration

Advantages: systemic side effects are rare.
Disadvantages: increased risk of systemic side effects if surfaces are large and/or inflamed.
Some topical anesthetics can be absorbed into the bloodstream.
Most effective on non-keratinized surfaces.

Topical Drug Examples

Creams, ointments, gels (epicutaneous)
Transdermal patches (fentanyl)
Sublingual tablets (NTG)
Buccal tablets
Subgingival (atridox, periochip)

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Description

Test your knowledge of pharmacokinetics with this quiz focusing on drug absorption, metabolism, distribution, and excretion. Explore key concepts such as half-life, onset, and various factors affecting drug behavior in the body. Perfect for students and professionals in pharmacy or related fields!