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Questions and Answers
What is the principal organ of drug metabolism?
What is the principal organ of drug metabolism?
Which component of the cytochrome P450 system is essential for its function?
Which component of the cytochrome P450 system is essential for its function?
What is first-pass metabolism primarily associated with?
What is first-pass metabolism primarily associated with?
Which of the following drugs is subject to extensive first-pass metabolism?
Which of the following drugs is subject to extensive first-pass metabolism?
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What contributes to the loss of drug doses during first-pass metabolism?
What contributes to the loss of drug doses during first-pass metabolism?
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Which of the following has the largest volume of total body water in a 70 kg adult?
Which of the following has the largest volume of total body water in a 70 kg adult?
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What is an effect of first-pass metabolism on orally administered drugs?
What is an effect of first-pass metabolism on orally administered drugs?
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Where does portal blood pass after being absorbed from the gastrointestinal tract?
Where does portal blood pass after being absorbed from the gastrointestinal tract?
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What does pharmacokinetics primarily refer to?
What does pharmacokinetics primarily refer to?
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Which of the following factors is NOT mentioned as influencing pharmacokinetic handling of a drug?
Which of the following factors is NOT mentioned as influencing pharmacokinetic handling of a drug?
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What outcome might result from impaired renal function according to pharmacokinetics?
What outcome might result from impaired renal function according to pharmacokinetics?
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Which aspect of drug response does pharmacodynamics specifically address?
Which aspect of drug response does pharmacodynamics specifically address?
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How can external factors like food influence pharmacokinetics?
How can external factors like food influence pharmacokinetics?
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What is a potential outcome of an excessive response to a drug?
What is a potential outcome of an excessive response to a drug?
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In pharmacokinetics, which factor is related to variability in drug responses among different patients?
In pharmacokinetics, which factor is related to variability in drug responses among different patients?
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What can lead to a suboptimal drug response during therapy?
What can lead to a suboptimal drug response during therapy?
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What occurs when a drug is administered at a high enough dose to saturate its primary metabolic pathway?
What occurs when a drug is administered at a high enough dose to saturate its primary metabolic pathway?
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What is the consequence of paracetamol overdose regarding its metabolism?
What is the consequence of paracetamol overdose regarding its metabolism?
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Why might the route of drug administration affect metabolism significantly?
Why might the route of drug administration affect metabolism significantly?
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What happens to a proportion of an orally administered drug?
What happens to a proportion of an orally administered drug?
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What is the primary organ responsible for excreting low molecular weight compounds?
What is the primary organ responsible for excreting low molecular weight compounds?
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Which of the following compounds is primarily excreted through bile?
Which of the following compounds is primarily excreted through bile?
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What is first-pass metabolism?
What is first-pass metabolism?
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How are drugs typically absorbed after oral administration?
How are drugs typically absorbed after oral administration?
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What is the primary focus of pharmacokinetics?
What is the primary focus of pharmacokinetics?
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Which phase of pharmacokinetics involves the body's handling of drugs after absorption?
Which phase of pharmacokinetics involves the body's handling of drugs after absorption?
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What does the acronym A-D-M-E in pharmacokinetics stand for?
What does the acronym A-D-M-E in pharmacokinetics stand for?
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Which of the following best describes pharmacodynamics?
Which of the following best describes pharmacodynamics?
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What is one key reason pharmacokinetics is important for prescribers?
What is one key reason pharmacokinetics is important for prescribers?
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Which organ is primarily involved in the metabolism of drugs?
Which organ is primarily involved in the metabolism of drugs?
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Which of the following best describes the relationship studied in pharmacokinetics?
Which of the following best describes the relationship studied in pharmacokinetics?
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How are drugs or their metabolites typically excreted from the body?
How are drugs or their metabolites typically excreted from the body?
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What does the law of mass action propose regarding chemical reactions?
What does the law of mass action propose regarding chemical reactions?
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How does drug concentration affect the metabolism of drugs in the cytochrome P450 system?
How does drug concentration affect the metabolism of drugs in the cytochrome P450 system?
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What does first-order kinetics imply in drug elimination processes?
What does first-order kinetics imply in drug elimination processes?
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What characterizes the drug elimination process for most drugs?
What characterizes the drug elimination process for most drugs?
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What relationship does glomerular filtration have with drug concentration in plasma?
What relationship does glomerular filtration have with drug concentration in plasma?
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How does increasing drug concentration affect the rate of elimination?
How does increasing drug concentration affect the rate of elimination?
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What happens to metabolic reactions as the concentration of reactants increases?
What happens to metabolic reactions as the concentration of reactants increases?
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What aspect of drug elimination does the law of mass action support?
What aspect of drug elimination does the law of mass action support?
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What does the elimination rate constant, k, help to describe in relation to drug concentration?
What does the elimination rate constant, k, help to describe in relation to drug concentration?
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What happens to plasma concentration after one half-life?
What happens to plasma concentration after one half-life?
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What is the relationship between dose increases and plasma concentration in first-order kinetics?
What is the relationship between dose increases and plasma concentration in first-order kinetics?
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What is a common characteristic of drugs that follow zero-order kinetics?
What is a common characteristic of drugs that follow zero-order kinetics?
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Which statement accurately reflects the implications of zero-order kinetics for prescribers?
Which statement accurately reflects the implications of zero-order kinetics for prescribers?
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In pharmacokinetics, what term is used to describe the time taken for the plasma concentration to halve?
In pharmacokinetics, what term is used to describe the time taken for the plasma concentration to halve?
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What can happen when a drug is administered at higher toxic doses?
What can happen when a drug is administered at higher toxic doses?
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Why is it said that for most drugs given in therapeutic doses, elimination is a first-order process?
Why is it said that for most drugs given in therapeutic doses, elimination is a first-order process?
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Study Notes
Pharmacokinetics
- Pharmacokinetics is the study of 'what the body does to a drug'
- It differentiates from pharmacodynamics (what a drug does to the body)
- It describes how the dosage regimen relates to the pharmacological effects
- It explains how drug concentration varies over time after administration
- It involves the rate and extent of drug absorption and distribution to body tissues
- It describes the rate and pathways by which drugs are eliminated from the body through metabolism and excretion
- It describes the relationship between time and plasma drug concentration
Learning Outcomes
- Explain what pharmacokinetics is
- Describe how drugs are absorbed into the body
- Describe how drugs are distributed in the body
- Describe how drugs are metabolised in the body
- Describe how drugs are excreted from the body
- Explain the relationship between drug concentration and time (single dose)
- Explain the relationship between drug concentration and time (repeated doses)
Four Phases of Pharmacokinetics
- Absorption of drugs into the body
- Distribution of drugs to the tissues
- Metabolism of drugs, notably in the liver
- Excretion of drugs, notably from the kidney
Routes of Drug Administration
- Oral (PO): drug swallowed
- Buccal: placed between the lip and gum
- Sublingual: placed beneath the tongue
- Rectal (PR): administered rectally
- Intravenous (IV): directly into a vein
- Intramuscular (IM): into muscle tissue
- Subcutaneous (SC): underneath the skin
- Inhalation (INH): via the airways
Oral Administration
- A proportion of the drug dose is bioavailable
- Drugs are affected by: gastric acid, food interactions, physicochemical characteristics
- First-pass metabolism (intestinal wall and liver) may limit absorption
Drug Distribution
- Drugs must reach the site of action at sufficient concentration
- Factors affecting distribution include: molecular size, lipid solubility, ionisation, binding to plasma proteins, rate of blood flow, and special barriers like the blood-brain barrier
- Drug concentrations in various body compartments (plasma, interstitial fluid, intracellular fluid) influence distribution
Drug Metabolism
- The liver is the principal organ of metabolism
- The cytochrome P450 system is a superfamily of enzymes in the smooth endoplasmic reticulum of hepatocytes
- The liver's anatomical relationship with the gastrointestinal tract impacts first-pass metabolism
- Other sites of metabolism include the lungs, kidneys, and skin
- Metabolism converts drugs into a less active or more water-soluble form for excretion
- Metabolism is categorized into Phase I and Phase II reactions
Drug Excretion
- The kidneys are the most important site for excretion of low molecular weight compounds
- Biliary excretion removes large molecular weight compounds
- Lungs excrete volatile anaesthetic gases and small amounts of other compounds
- Other excretion routes include tears, sweat, saliva, and breast milk
Drug Concentration and Time (Single Dose)
- First-order kinetics: The rate of elimination is proportional to the drug concentration.
- Zero-order kinetics: The rate of elimination is constant, regardless of the drug concentration (common in high doses).
Drug Concentration and Time (Repeated Doses)
- Repeated doses lead eventually to a steady state, where the rate of drug administration equals the rate of drug elimination.
- Steady state is reached after 5 half-lives.
- Factors affecting repeated dose pharmacokinetics include half-life and dosing interval.
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Description
This quiz explores the fundamental concepts of pharmacokinetics, including drug absorption, distribution, metabolism, and excretion. Understand the relationship between drug concentration and time to master how the body interacts with medications. Ideal for students in pharmacology or related fields.
