Questions and Answers
What is meant by the term 'absorption' in pharmacokinetics?
Which factor does NOT affect the rate of absorption of a drug?
What occurs to a receptor upon ligand binding?
What is the primary organ responsible for the metabolism of drugs?
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Which statement is true regarding hydrophilic and hydrophobic ligands?
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Which statement accurately describes the term 'distribution' in pharmacokinetics?
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What type of receptors are responsible for the rapid flow of ions across cell membranes?
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Why is IV delivery considered complete in terms of absorption?
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What determines the bioavailability of a drug delivered by non-IV routes?
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What major receptor family interacts with hydrophilic ligands?
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Which statement is NOT true about the plasma membrane's role in drug movement?
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Which of the following represents a characteristic of G protein-coupled receptors?
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Which characteristic of a drug does NOT predict its movement and availability at the sites of action?
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Which receptor family is characterized by their involvement in rapid ion flow regulation?
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Which of the following is a correct example of a ligand-gated ion channel?
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What does pharmacology define as a receptor?
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What primarily determines the rate at which highly lipid-soluble drugs cross lipid membranes?
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What is the pH range of the stomach that affects drug ionization?
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Which factor is NOT mentioned as influencing drug absorption?
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What equation is used to determine the relationship between pKa and pH for drug distribution across membranes?
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How does blood flow to the intestine compare to that of the stomach?
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What happens to drug absorption during severe diarrhea?
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What is the primary reason the intestine is more efficient in drug absorption than the stomach?
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What impact does an increase in drug contact time at the absorption surface have?
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What effect does grapefruit juice have on drugs metabolized by CYP3A4?
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Which of the following is NOT a Phase I reaction in drug metabolism?
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What can result from the inhibition of drug metabolism over time?
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Which drug is an example of one that is conjugated in Phase II metabolism?
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Which statement about neonates and drug metabolism is true?
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Which of the following statements about drug metabolism phases is inaccurate?
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Which Phase I reaction is specifically an oxidation of catecholamines?
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What is the primary outcome of glucuronidation in drug metabolism?
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What is the estimated percentage of 'spare' receptors in insulin receptors?
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Which of the following statements about the human heart's β-adrenoceptors is correct?
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What phenomenon occurs when repeated drug administration leads to diminished receptor responsiveness?
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Which of the following mechanisms is NOT a method of receptor desensitization?
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After stimulation, voltage-gated channels require what type of phase before they can be activated again?
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Which statement best describes an agonist?
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What happens to receptors during down-regulation?
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What is the main implication of having few spare receptors in the failing heart?
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Study Notes
Pharmacokinetics Overview
- Pharmacokinetics studies the body's effect on drugs, encompassing absorption, distribution, metabolism, and excretion (ADME).
- Absorption involves transferring a drug from its administration site to the bloodstream through various membrane barriers.
- Distribution occurs via circulatory and lymphatic systems, affecting drug availability at action sites.
- Metabolism primarily happens in the liver (hepatic), with two main phases: Phase I (chemical modification) and Phase II (conjugation for elimination).
- Excretion occurs via kidneys, liver, or feces, influenced by drug polarity and solubility.
Drug Absorption
- The rate and efficiency of absorption depend on the route, with intravenous (IV) administration achieving complete absorption.
- Oral administration may result in partial absorption influenced by the drug's solubility and physiological factors, such as food presence.
- Non-ionized forms of drugs, particularly weak bases, diffuse through lipid membranes effectively.
Factors Affecting Absorption
- Blood Flow: Increased intestinal blood flow enhances absorption versus the stomach.
- Surface Area: The extensive microvilli in the intestines create a large surface area for efficient absorption.
- Contact Time: Rapid transit through the GI tract (e.g., diarrhea) reduces absorption efficiency; delays in gastric emptying increase it.
Drug Metabolism
- Phase I Metabolism: Involves oxidation, hydrolysis, and reduction; can lead to increased drug levels over time due to inhibition.
- Phase II Metabolism: Involves conjugation, producing polar metabolites for excretion. Morphine-6-glucuronide is a notable exception with higher potency.
- Not all drugs follow a strict Phase I then Phase II order; some undergo reverse phases based on metabolic pathways.
Receptor Families in Pharmacodynamics
- Receptors are biological molecules where drugs bind to produce measurable effects.
- Major receptor families include:
- Ligand-gated ion channels (rapid response)
- G protein-coupled receptors (cell surface interaction)
- Enzyme-linked receptors (kinase activation)
- Intracellular receptors (lipid-soluble ligand interaction)
Receptor Activation and Response
- Agonists bind to receptors, eliciting biological responses; the interaction type dictates the receptor family involved.
- Spare receptors exist, providing functional reserve; insulin receptors show around 99% spareness, while β-adrenoceptors have much less.
Desensitization of Receptors
- Continuous agonist or antagonist exposure can lead to decreased receptor responsiveness, termed tachyphylaxis.
- Receptors may undergo endocytosis and be sequestered or down-regulated, leading to decreased availability and sensitivity.
- Some receptors require rest periods post-stimulation before they become responsive again, entering a refractory state.
Dose-Response Relationships
- Agonists are defined as agents binding to receptors to elicit biological responses, forming the basis for understanding drug efficacy and potency.
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Description
This quiz covers the fundamental concepts of pharmacokinetics, focusing on the processes of absorption, distribution, metabolism, and elimination (ADME) of drugs. Understand how drugs interact with the body and the consequences of these interactions on their effectiveness. Test your knowledge of how pharmacokinetic principles apply in clinical settings.
