Veterinary Pharmacology: ADME Principles

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Questions and Answers

What factor does NOT influence the distribution of a drug in the body?

Local temperature (correct)

Blood flow

Transport mechanisms

Physicochemical characteristics of the drug

Which statement correctly describes unbound (free) drug?

It has no effect on the body

It binds to proteins in the blood

It is always inactive

It can distribute into tissues (correct)

What genetic factor can affect drug distribution and individual variation in drug response?

Changes in body mass index

Mutations in P-glycoprotein transporters (correct)

Variations in liver enzymes

Altered kidney function

Which compartment is initially involved in drug distribution?

Central compartment Signup and view all the answers

Which one of the following could potentially limit drug distribution into a specific tissue?

High protein binding within the tissue Signup and view all the answers

Which of the following is NOT a component of phase 1 or phase 2 drug metabolism?

Protein binding Signup and view all the answers

How does a genetic mutation in the MDR-1 gene affect drug treatment for cancer?

Contributes to drug resistance Signup and view all the answers

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

Helps in drug excretion Signup and view all the answers

What is the primary route of drug elimination in the body?

Kidneys Signup and view all the answers

Which of the following processes does NOT contribute to drug elimination by the kidneys?

Biliary excretion Signup and view all the answers

How can drug metabolites excreted in bile affect the body?

They can be reabsorbed from the intestine. Signup and view all the answers

What effect does urinary pH have on drug elimination?

It can influence the rate of renal excretion of ionisable drugs. Signup and view all the answers

Which of the following species has a renal portal system that affects drug elimination?

Birds and reptiles Signup and view all the answers

Which of the following is NOT a method of drug elimination mentioned?

Fermentation Signup and view all the answers

What should be considered when treating a patient with chronic kidney disease regarding drug dosing?

Doses may need to be adjusted according to the drug. Signup and view all the answers

What impact does high reabsorption of water from avian excreta have?

Increases susceptibility to toxicosis. Signup and view all the answers

Which of the following is NOT a common route of drug administration in veterinary medicine?

Inhalation Signup and view all the answers

What factor does NOT influence the choice of drug administration route?

Time of day Signup and view all the answers

What role does absorption play in the pharmacokinetic process?

It is the process of a drug moving to the systemic circulation. Signup and view all the answers

Which barrier is specifically mentioned as a restriction in drug distribution?

Blood-brain barrier Signup and view all the answers

In the pharmacokinetic process, what is the primary purpose of metabolism?

To transform drugs into inactive forms or metabolites Signup and view all the answers

Which of the following statements about drug elimination is true?

It can involve both kidneys and liver. Signup and view all the answers

Phase 1 metabolic reactions typically involve which of the following?

Hydrolysis and oxidation reactions Signup and view all the answers

Species differences in pharmacokinetics can significantly affect which aspect of drug use?

The speed of drug absorption and metabolism Signup and view all the answers

What is the primary role of cytochrome P450 enzymes in drug metabolism?

To introduce reactive chemical groups to drugs Signup and view all the answers

Which of the following best describes Phase 1 reactions in drug metabolism?

They introduce reactive chemical groups to form more reactive metabolites Signup and view all the answers

How do Phase 2 reactions differ from Phase 1 reactions in drug metabolism?

Phase 2 reactions usually result in inactive, polar products Signup and view all the answers

What characterizes lipophilic drugs in relation to kidney excretion?

They must be metabolized to polar products for excretion Signup and view all the answers

What type of transformation does biotransformation refer to?

The chemical alteration of drug molecules Signup and view all the answers

What is the primary factor influencing the route of drug administration in veterinary medicine?

Desired speed of onset of drug action Signup and view all the answers

What is the common outcome of Phase 2 reactions for most drugs?

They become inactive and polar for easier excretion Signup and view all the answers

Which of the following factors does NOT influence drug uptake?

Color of the drug Signup and view all the answers

Which of the following groups is commonly inserted during Phase 2 reactions?

Glucuronyl or acetate groups Signup and view all the answers

What process allows a drug to move from its site of administration into systemic circulation?

Uptake Signup and view all the answers

What role does molecular size play in drug uptake?

Larger molecules typically have reduced absorption Signup and view all the answers

What is a potential effect of drug metabolites on biological systems?

Some metabolites can be biologically active Signup and view all the answers

Which anatomic barrier significantly restricts drug distribution?

Blood-brain barrier Signup and view all the answers

Which factor does NOT directly affect drug distribution?

Drug's color Signup and view all the answers

What is one of the main biological factors affecting drug absorption?

Local blood flow Signup and view all the answers

Which route of drug administration is generally considered the fastest?

Intravenous Signup and view all the answers

What is a significant reason why paracetamol should not be given to cats?

Cats have very low glucuronidation capacity. Signup and view all the answers

What is described as the process that alters the action and/or kinetics of a drug?

Drug interaction Signup and view all the answers

What could be a consequence of first-pass metabolism when administering drugs orally?

Lower plasma concentrations than when given intravenously. Signup and view all the answers

In Snowy's case, what is likely to happen to the plasma levels of cyclosporine when treated with ketoconazole?

Increase due to competition in metabolism. Signup and view all the answers

Which of the following best describes drug elimination?

The removal of drug from the body through metabolic and/or excretory processes. Signup and view all the answers

Which factor is NOT associated with first-pass metabolism?

Age of the individual Signup and view all the answers

Why might higher doses be required when a drug is given orally?

Some of the drug is lost during gastrointestinal processing. Signup and view all the answers

How does a fungal infection in Snowy affect the treatment with cyclosporine?

It may require increased doses of cyclosporine. Signup and view all the answers

Study Notes

ADME (Absorption, Distribution, Metabolism, Elimination)

Absorption is the process where a drug moves from its site of administration to the systemic circulation.
Drugs cross cell membranes (lipid bilayers) using passive diffusion, solute carrier-mediated transport or diffusion through aqueous pores.
Factors affecting drug uptake include chemical properties (e.g., solubility, size, ionization), and biological factors (e.g., vascularity, local blood flow, pH, enzymes).
The most common routes of administration in veterinary medicine are oral, intravenous, intramuscular, subcutaneous, and topical.
Species differences, disease state, mentation state, practicality and safety, desired speed of onset, type of disease (local or systemic), and cost influence choice of route.

Drug Distribution

Drug distribution is the reversible movement of a drug between tissues, organs, and compartments.
Drugs are distributed throughout the body via bulk flow in the blood; the gaps between vascular endothelial cells let drugs with a molecular weight of less than 1000 Da to leave blood vessels.
The blood-brain barrier and placenta have tightly-connected junctions that prevent penetration by harmful substances.
Drug distribution can be affected by reversible protein binding in the plasma; only unbound (free) drug is able to distribute to tissues.
Drug distribution occurs initially in a central compartment (plasma and highly perfused tissues) before moving to peripheral tissues.
Local pH, blood flow, transport mechanisms, disease processes, and protein binding affect distribution.
Individual variation in drug response can differ based on genetic mutations affecting P-glycoprotein transporters which change the concentration and distribution of drugs.

Drug Metabolism

Drug metabolism is the chemical transformation of a drug to one or more products in the body.
Polar drugs can be eliminated unchanged through the kidneys.
Lipophilic drugs must be metabolised to more polar products in order to be eliminated.
Liver cytochrome P450 (CYP450) enzymes are primarily responsible for drug metabolism.
Drug metabolism involves two types of reactions:
- Phase 1 reactions (catabolic) - introduce a reactive group (e.g., hydroxyl, oxydation, reduction)
- Phase 2 reactions (anabolic) - involve conjugation (attach a polar group like glucuronic acid) to make drug more excretable and less active.
Species differences in drug metabolism can cause drug effects to be different.
First-pass metabolism is the metabolism of a drug by gut and liver enzymes before it enters systemic circulation, dramatically decreasing the bioavailability of an orally administered drug.

Drug Elimination

Drug elimination is the irreversible removal of a drug from the body through metabolic and/or excretory processes.
Kidneys are a main route for drug elimination, and renal function greatly affects plasma concentrations and duration of action.
Drug elimination can also occur in the digestive tract (biliary excretion), exhaled air (volatile anaesthetics), milk, sweat, tears, and saliva.
Species differences in elimination routes such as renal portal systems, or high water reabsorption in avians can exist.
Drug elimination can follow enterohepatic recycling (reabsorption from the gut after excretion in bile).
Drug interactions can affect elimination processes, by competing for the same elimination pathways.

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Description

This quiz focuses on the fundamental principles of ADME (Absorption, Distribution, Metabolism, Elimination) in veterinary pharmacology. It covers how drugs are absorbed into the systemic circulation and the factors affecting their uptake, along with the mechanisms of distribution within the body. Participants will also explore the common routes of drug administration and their implications in different species.