Fundamentals of Pharmacology Lectures 6-11

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Questions and Answers

Which tissues are considered to have high perfusion rates, allowing for faster drug distribution?

Skin and fat

Liver and kidney (correct)

Bone and resting muscle

Nervous system and adipose tissue

Which statement correctly describes the relationship between plasma protein binding and drug activity?

All drug molecules can pass cell membranes regardless of binding.

Bound drugs are more effective in reaching target tissues.

Only bound drug molecules can interact with receptors.

Only free drug molecules can pass cell membranes and interact with receptors. (correct)

What effect does increased blood flow have on drug distribution?

It slows down drug distribution.

It enables a greater number of drug molecules to enter organs. (correct)

It has no impact on the rate of distribution.

It decreases the plasma concentration of the drug.

How does the drug distribution pattern change during shock?

Circulatory collapse slows drug elimination and alters drug distribution. Signup and view all the answers

What unique consideration must be taken into account for drug dosing in neonates?

Neonates generally require a higher dose since they have a larger water content and lower plasma protein binding. Signup and view all the answers

What is a consequence of being an ultra-rapid metabolizer?

No drug response at ordinary doses Signup and view all the answers

Which of the following statements about poor metabolizers is true?

They often incur a high risk of toxicity. Signup and view all the answers

What primarily causes differences in enzyme activity across species?

Genetic differences and availability of enzymes Signup and view all the answers

How is the first pass effect particularly significant for drugs taken orally?

It can reduce the therapeutic effect of the drug. Signup and view all the answers

Which of the following drugs is particularly toxic to cats due to their metabolic capacity?

Ibuprofen Signup and view all the answers

What process can lead to altered first pass metabolism?

Induction or inhibition of metabolic enzymes Signup and view all the answers

What occurs during kidney excretion?

Filtration, secretion, and reabsorption processes Signup and view all the answers

What is a characteristic of extensive metabolizers?

They experience the expected drug response. Signup and view all the answers

What process describes the movement of drug molecules from the renal tubules back into the circulatory system?

Drug reabsorption Signup and view all the answers

Which factor can significantly affect the rate of drug elimination?

Presence of biliary disease Signup and view all the answers

Which of the following best describes the nature of drug filtration in the kidneys?

Passive process through the glomerulus Signup and view all the answers

How does enterohepatic recycling influence drug treatment plans?

It can alter plasma concentrations of drugs. Signup and view all the answers

What is the main purpose of drug secretion in the kidneys?

To actively transport drugs to the renal tubules Signup and view all the answers

Which statement about biliary excretion is correct?

It involves active transport of polar substances. Signup and view all the answers

Which type of drug is likely to be better excreted in breast milk?

Basic drugs Signup and view all the answers

What clinical application can be derived from understanding drug excretion?

Optimizing drug dosing regimens Signup and view all the answers

What does the parameter F primarily help to calculate when administering a drug via an EV dose?

The dosage needed based on the IV dose Signup and view all the answers

Which of the following factors can decrease the bioavailability of a drug?

Dehydration leading to decreased blood flow Signup and view all the answers

What is the primary significance of clearance in pharmacokinetics?

It indicates the volume of plasma totally cleared of drug per unit time Signup and view all the answers

Which of the following statements about clearance is correct?

Clearance remains constant under linear pharmacokinetic conditions Signup and view all the answers

Which scenario might cause an increase in the bioavailability of a drug?

First-pass metabolism being reduced due to liver disease Signup and view all the answers

What is the significance of the Margin of Safety (MOS) in pharmacology?

It indicates the difference between effective and toxic doses. Signup and view all the answers

Which physiological process is NOT one of the four key processes governing drug movement in the body?

Decomposition Signup and view all the answers

How does lipid solubility affect drug absorption?

Higher lipid solubility increases the rate of absorption. Signup and view all the answers

What is the main role of drug absorption in pharmacokinetics?

To delay the appearance of drugs in the blood. Signup and view all the answers

What happens to the extent of drug absorption when local blood flow is decreased?

It decreases. Signup and view all the answers

Which statement accurately describes the factors affecting drug absorption?

Molecular size affects the ease of drug absorption. Signup and view all the answers

In pharmacokinetics, what does ADME stand for?

Absorption, Distribution, Metabolism, Excretion Signup and view all the answers

What property of drugs influences their ionization state and consequently their absorption?

Chemical nature of the drug. Signup and view all the answers

Which statement is true regarding drug administration routes?

Some routes bypass the absorption phase completely. Signup and view all the answers

What is the impact of drug ionization on absorption?

Only non-ionized drugs can cross cell membranes. Signup and view all the answers

Study Notes

Variability in Clinical Response

Average drug doses may not be safe or effective for all individuals due to variability in response.
Determining proper drug dosage is critical to avoid adverse effects.

Tenets in Pharmacology

Drug molecules must be present at the site of action in sufficient concentration for a defined duration to yield pharmacological effects.

Pharmacokinetics Overview

Pharmacokinetics examines the time course of drug concentrations in the body, encompassing absorption, distribution, metabolism, and excretion (ADME).
Margin of Safety (MOS) is the range between minimum and maximum effective drug concentrations.

Drug Absorption

Drug absorption is the transition from the administration site into systemic circulation, except for intravascular routes.
Rate and extent of absorption influence onset of action and plasma concentration, which correlate with drug effects.

Factors Influencing Drug Absorption

Anatomical Barriers: Types of transport (passive, facilitated, active) affect drug movement across membranes.
Local Blood Flow: Increased blood flow enhances drug absorption; decreased flow reduces it.
Chemical Properties: Lipid solubility, molecular size, and ionization state (only non-ionized drugs cross membranes) impact absorption.
Route of Administration: Varying absorption rates based on the route; first-pass metabolism for orally administered drugs.

Distribution

Drug distribution depends on blood flow to tissues; higher perfusion rates (e.g., CNS, liver) enhance absorption and distribution.
Factors such as shock, exercise, and developmental stages (e.g., in neonates) affect distribution patterns.

Drug Metabolism Variability

Variability in drug metabolism is influenced by genetic factors, leading to different metabolizer categories: ultra-rapid, extensive, intermediate, and poor metabolizers.
Metabolism rate impacts drug response, toxicity, and required dosing adjustments.

First Pass Effect

Occurs when drugs undergo metabolism prior to entering systemic circulation, significantly affecting bioavailability, especially for oral drugs.
Influenced by liver biotransformation capacity.

Drug Excretion Mechanisms

Kidneys: Filtration, secretion, and reabsorption help regulate drug elimination.
Factors like transport proteins can lead to drug-drug interactions affecting excretion rates.

Biliary and Enterohepatic Excretion

Biliary excretion involves water-soluble, high molecular weight drugs; changes in transport can alter plasma concentrations.
Enterohepatic recycling can be impacted by biliary or liver diseases, necessitating dosage adjustments.

Alternative Excretion Pathways

Inhalation eliminates anesthetic gases.
Mammary excretion favors basic drugs; may expose neonates to drugs.
Less significant pathways include sweat and saliva but can still have clinical implications.

Bioavailability Factors

Increased Bioavailability: Liver disease and enzyme inhibition can improve oral drug absorption.
Decreased Bioavailability: Induction of enzymes, gastrointestinal disease, and dehydration can hinder absorption efficiency.

Clearance

Clearance is a vital pharmacokinetic parameter reflecting the rate at which drugs are eliminated relative to plasma concentration.
It is crucial in determining the necessary dosage and frequency of administration, as it remains constant under linear kinetics and plays a key role in the pharmacokinetics of any drug.

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Description

This quiz covers essential concepts from lectures 6 to 11 of the pharmacology course, focusing on pharmacokinetics and pharmacodynamics. It explores factors influencing variability in clinical responses and the implications for drug dosing. Prepare to assess your understanding of these core topics in pharmacology!