Biopharmaceutics & Pharmacokinetics Week 4 Quiz

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Questions and Answers

What is the primary purpose of metabolism in the body?

To synthesize new drugs

To store nutrients for future use

To supply energy for body functions (correct)

To eliminate waste from the body

Which organ is identified as the principal site of metabolism?

Kidney

Heart

Lungs

Liver (correct)

Enzymatic transformation of drugs generally results in products that are:

More toxic than the original substance

Similar in chemical structure to the original drug

Unable to be eliminated from the body

Less toxic and more readily excreted (correct)

What does the term 'xenobiotics' refer to?

Foreign chemicals ingested or produced by the body Signup and view all the answers

Which of the following is NOT a principal purpose of metabolism?

Producing waste for elimination Signup and view all the answers

Which component carries oxygenated blood to the liver?

Hepatic artery Signup and view all the answers

What is the role of the hepatic portal vein?

To collect blood from the gastrointestinal tract for nutrient delivery to the liver Signup and view all the answers

What is a key idea regarding drug metabolizing enzymes?

They can influence drug action and therapeutic outcomes Signup and view all the answers

What effect does phenobarbital have on the metabolism of other drugs when given repeatedly?

Increases metabolism of other drugs Signup and view all the answers

Which of the following is NOT classified as an enzyme inducer?

Cimetidine Signup and view all the answers

How do enzyme inhibitors affect drug metabolism?

Decrease drug metabolism and increase drug effects Signup and view all the answers

What is the primary impact of first pass effect on drug availability?

Reduces systemic availability of the drug Signup and view all the answers

What is a significant neurotoxic effect of Phenytoin that Ms. Danvers experienced after starting Isoniazid?

Ataxia and slurred speech Signup and view all the answers

Which of the following best defines clearance in the context of drug elimination?

The volume of fluid cleared of drug from the body per unit of time Signup and view all the answers

What pathways are primarily involved in the excretion of nonvolatile drugs?

Kidneys and urine Signup and view all the answers

Which of the following substances is classified as an enzyme inhibitor?

Ketoconazole Signup and view all the answers

What role does renin play in kidney function?

Regulates blood pressure Signup and view all the answers

Which part of the nephron is responsible for the majority of tubular reabsorption?

Proximal convoluted tubule Signup and view all the answers

What is the primary function of the glomerulus in the kidney?

Filtration of small molecules Signup and view all the answers

How does renal blood flow relate to vascular resistance?

Indirectly proportional Signup and view all the answers

Which process in the kidney involves the removal of metabolic waste?

Tubular secretion Signup and view all the answers

What role do sinusoids play in the metabolism of drugs and nutrients?

They facilitate drug and nutrient removal before blood reaches general circulation. Signup and view all the answers

Which type of metabolite is Procaine converted into?

p-aminobenzoic acid Signup and view all the answers

What characterizes metabolites that retain similar activity?

They maintain similar therapeutic effects as their parent drug. Signup and view all the answers

Which of the following is a reactive metabolite?

Acetaminophen Signup and view all the answers

Which metabolite conversion is an example of a bioactivated metabolite?

Sulindac to active sulfide Signup and view all the answers

What is a common feature of drug metabolites compared to their parent drugs?

They are more ionized and less lipid soluble. Signup and view all the answers

Which of the following statements accurately describes altered activity metabolites?

They exhibit a changed pharmacological effect compared to the parent drug. Signup and view all the answers

What is one of the three major components of drug biotransformation?

Product Signup and view all the answers

What is the main consequence of increased drug doses in sulfate conjugation?

Saturation of sulfate conjugation Signup and view all the answers

Which enzyme is primarily responsible for the methylation process in drug metabolism?

Methyl transferase Signup and view all the answers

At what age is acetylation capacity considered to be developed in infants?

At one month Signup and view all the answers

Which conjugation method is most common for aromatic heterocyclic carboxylic acid drugs?

Glycine conjugation Signup and view all the answers

What characterizes enzyme induction?

Stimulated increase in enzyme activity Signup and view all the answers

Which population characteristic affects the expression of acetyl transferase?

Genetic polymorphism Signup and view all the answers

What is the primary function of glutathione conjugation in metabolism?

Detoxification of free radicals Signup and view all the answers

What is formed from the reaction of S-adenosylmethionine in the methylation process?

Methylated drugs Signup and view all the answers

Which two conjugation processes are not fully developed at birth but are progressively matured?

Acetylation and glucuronidation Signup and view all the answers

What is the effect of auto-induction in drug metabolism?

Stimulation of its own metabolism Signup and view all the answers

Study Notes

Metabolism Overview

Metabolism, also referred to as biotransformation, involves enzymatic or biochemical transformation of drugs into less toxic metabolites for easier elimination.
Drug metabolism is a chemical process facilitated by the biological environment, aiming to supply energy, break down foreign compounds, and increase water solubility.

Liver Function and Structure

The liver is the principal organ responsible for metabolism, acting as both a synthesizing and eliminating organ.
Liver anatomy includes the liver lobule as the basic structural unit, hepatic artery for oxygen-rich blood, and hepatic portal vein for nutrient-rich blood.

Metabolizing Enzymes

Drug metabolism occurs in various liver fractions, including soluble, mitochondrial, and microsomal.
Some metabolism can also occur in the bloodstream due to enzyme leakage from cells.

Classes of Metabolites

Inactive metabolites decrease pharmacological action (e.g., Procaine to p-aminobenzoic acid).
Metabolites retaining similar activity continue to exert effects (e.g., Codeine to Morphine).
Metabolites with altered activity (e.g., Iproniazid to isoniazid) may have different effects than the parent drug.
Bioactivated metabolites are inactive until converted (e.g., Enalapril to Enalaprilat).
Reactive metabolites can potentially be toxic (e.g., Acetaminophen to NAPQI).

Biotransformation Components

Three major components involved in drug biotransformation are the reactant (the drug), the product (the metabolite), and the treatment provided.

Conjugation Pathways

Sulfate Conjugation: Enzyme sulfotransferases in liver, kidney, and GI tract; limited capacity and easily saturated at high doses.
Methylation: A minor pathway involving methyl transferase, significant for endogenous substances.
Acetylation: Catalyzed by acetyl transferases; genetics influence speed of metabolism (slow vs. fast acetylators).
Glutathione Conjugation: Detoxifies reactive oxygen species; critical in cellular protection.
Amino Acid Conjugation: Glycine and Glutamine play roles in conjugation with organic acids.

Maturation of Metabolic Processes in Infants

Metabolic capacity develops over time with significant processes emerging at various ages, such as sulfation at birth and glucuronidation around two months.

Enzyme Induction and Inhibition

Enzyme Induction: Increased enzyme activity speeds metabolism; it is an adaptation to exogenous substances.
Enzyme Inhibition: Results in decreased enzyme activity, leading to increased drug effects due to slower metabolism.

First Pass Effect

Describes pre-systemic metabolism where drugs undergo transformation before systemic circulation, often reducing their bioavailability.

Excretion Mechanisms

Excretion finalizes drug removal from the body through various routes including renal (urine), fecal, and respiratory pathways for volatile compounds.

Clearance

Clearance reflects the rate of drug elimination from the body, measured in volume over time (mL/min or L/hr).
The kidney plays a vital role, maintaining fluid balance and producing essential hormones like renin and erythropoietin.

Kidney Function

Three main processes in kidney function include glomerular filtration (passive), active tubular secretion, and tubular reabsorption necessary for waste removal and electrolyte balance.

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Description

Test your knowledge on the principles and factors of metabolism in pharmacokinetics. This quiz covers various metabolic pathways, drug metabolizing enzymes, and their implications on drug action. Prepare to identify key enzyme inducers and their roles in drug metabolism.