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Questions and Answers
What is the primary determinant of drug distribution throughout the body?
What is the primary determinant of drug distribution throughout the body?
- Volume of body fluids (correct)
- Patient's age
- Drug metabolism rate
- Rate of excretion
A drug that is highly confined to the vascular compartment is expected to have:
A drug that is highly confined to the vascular compartment is expected to have:
- A small volume of distribution (Vd) (correct)
- Minimal plasma protein binding
- Extensive tissue distribution
- A large volume of distribution (Vd)
What does a large volume of distribution (Vd) suggest about drug distribution?
What does a large volume of distribution (Vd) suggest about drug distribution?
- The drug is rapidly excreted
- The drug is strongly bound to plasma proteins
- The drug has extensive tissue distribution (correct)
- The drug is mainly present in the vascular compartment
In cases of drug toxicity, hemodialysis is most effective for drugs with:
In cases of drug toxicity, hemodialysis is most effective for drugs with:
Which plasma protein primarily binds to drugs?
Which plasma protein primarily binds to drugs?
Hypoalbuminemia can impact drug distribution in what way?
Hypoalbuminemia can impact drug distribution in what way?
What is a consequence of a drug being highly bound to plasma proteins?
What is a consequence of a drug being highly bound to plasma proteins?
Why is only the free (unbound) fraction of a drug considered pharmacologically active?
Why is only the free (unbound) fraction of a drug considered pharmacologically active?
A drug that reduces the binding of warfarin to plasma proteins could result in what?
A drug that reduces the binding of warfarin to plasma proteins could result in what?
Why do non-ionized, highly lipid-soluble drugs readily cross the blood-brain barrier (BBB)?
Why do non-ionized, highly lipid-soluble drugs readily cross the blood-brain barrier (BBB)?
What type of drugs can cross the placental barrier and potentially harm the fetus?
What type of drugs can cross the placental barrier and potentially harm the fetus?
Why do basic drugs accumulate in breast milk?
Why do basic drugs accumulate in breast milk?
What happens during redistribution of drugs like thiopental?
What happens during redistribution of drugs like thiopental?
What primarily determines the duration of action of thiopental?
What primarily determines the duration of action of thiopental?
What is the main site of drug metabolism in the body?
What is the main site of drug metabolism in the body?
Drug metabolism can result in the production of:
Drug metabolism can result in the production of:
What is a prodrug?
What is a prodrug?
In general terms, what is 'volume of distribution'?
In general terms, what is 'volume of distribution'?
A patient has taken an overdose of a drug known to have a high volume of distribution. How would the high Vd affect the efficacy of dialysis?
A patient has taken an overdose of a drug known to have a high volume of distribution. How would the high Vd affect the efficacy of dialysis?
Considering clinical significance of Vd, which is more likely to occur with a drug that has small Vd?
Considering clinical significance of Vd, which is more likely to occur with a drug that has small Vd?
A new drug is developed that is found to be 99% bound to plasma proteins. What implication can this information tell you about the drug?
A new drug is developed that is found to be 99% bound to plasma proteins. What implication can this information tell you about the drug?
Why is it important to consider the pH difference between plasma and breast milk regarding drug administration to lactating mothers?
Why is it important to consider the pH difference between plasma and breast milk regarding drug administration to lactating mothers?
How does first-generation antihistaminics being administered to lactating mothers affect the baby?
How does first-generation antihistaminics being administered to lactating mothers affect the baby?
If a drug's duration of action depends on redistribution rather than metabolism or excretion, which is most likely?
If a drug's duration of action depends on redistribution rather than metabolism or excretion, which is most likely?
Upon entering the blood, drugs may bind plasma proteins. A drug that follows this phenomena is:
Upon entering the blood, drugs may bind plasma proteins. A drug that follows this phenomena is:
What is something to consider upon administering drugs to a breastfeeding mother?
What is something to consider upon administering drugs to a breastfeeding mother?
What affect does starvation or malnutrition have on free drug?
What affect does starvation or malnutrition have on free drug?
Which of the following statements best describes the clinical implications of a drug with a small Vd?
Which of the following statements best describes the clinical implications of a drug with a small Vd?
A patient with liver cirrhosis exhibits decreased albumin levels. How might this condition affect the pharmacokinetics of a highly protein-bound drug?
A patient with liver cirrhosis exhibits decreased albumin levels. How might this condition affect the pharmacokinetics of a highly protein-bound drug?
A drug is known to undergo significant redistribution. What effect would increased body fat percentage have on the drugs half life?
A drug is known to undergo significant redistribution. What effect would increased body fat percentage have on the drugs half life?
Considering all other drug factors being the same among a group of patients of varying body weights, what would be the affect of the patient with the lowest bloodflow to an organ?
Considering all other drug factors being the same among a group of patients of varying body weights, what would be the affect of the patient with the lowest bloodflow to an organ?
A patient is administered a drug that is able to pass through the placenta. What is a possible side effect?
A patient is administered a drug that is able to pass through the placenta. What is a possible side effect?
A patient taking warfarin is prescribed a new drug that displaces warfarin from its binding sites on plasma proteins. What is the most likely outcome?
A patient taking warfarin is prescribed a new drug that displaces warfarin from its binding sites on plasma proteins. What is the most likely outcome?
A drug is eliminated primarily through biotransformation in the liver. How might severe liver disease affect its elimination?
A drug is eliminated primarily through biotransformation in the liver. How might severe liver disease affect its elimination?
A drug is known to be a substrate of a specific CYP450 enzyme. Co-administration of a drug that potently inhibits this enzyme would likely result in:
A drug is known to be a substrate of a specific CYP450 enzyme. Co-administration of a drug that potently inhibits this enzyme would likely result in:
A drug is actively transported into hepatocytes (liver cells) by a specific transporter protein. A genetic polymorphism leads to reduced expression of this transporter. What would be the consequence?
A drug is actively transported into hepatocytes (liver cells) by a specific transporter protein. A genetic polymorphism leads to reduced expression of this transporter. What would be the consequence?
A drug is almost entirely renally excreted. A patient with severe renal impairment is prescribed this medication. The physician should:
A drug is almost entirely renally excreted. A patient with severe renal impairment is prescribed this medication. The physician should:
An exceptionally obese patient is prescribed an anesthetic with a high-lipid solubility. What alteration to the normal dosing schedule would be most appropriate?
An exceptionally obese patient is prescribed an anesthetic with a high-lipid solubility. What alteration to the normal dosing schedule would be most appropriate?
You administer a new drug to a patient intravenously and notice that its plasma concentration declines rapidly in a biphasic manner: a steep initial decline followed by a slower decline. This observation is most consistent with:
You administer a new drug to a patient intravenously and notice that its plasma concentration declines rapidly in a biphasic manner: a steep initial decline followed by a slower decline. This observation is most consistent with:
Which of the following scenarios would lead to the MOST significant increase in the risk Torsades de Pointes (a fatal heart condition) when administering Sotalol, in the absence of lab monitoring?
Which of the following scenarios would lead to the MOST significant increase in the risk Torsades de Pointes (a fatal heart condition) when administering Sotalol, in the absence of lab monitoring?
An experimental drug has been designed to target a specific intracellular protein within neurons. Which of the properties would be MOST crucial for this drug to effectively reach its target?
An experimental drug has been designed to target a specific intracellular protein within neurons. Which of the properties would be MOST crucial for this drug to effectively reach its target?
Flashcards
Distribution
Distribution
The process by which a drug reversibly leaves the bloodstream and enters the tissues and organs of the body.
Apparent Volume of Distribution (Vd)
Apparent Volume of Distribution (Vd)
The theoretical volume that would be necessary to contain the total amount of an administered drug at the same concentration that it is observed in the blood plasma.
Small Vd implication
Small Vd implication
Drugs with a small Vd are primarily confined to the vascular compartment, with minimal tissue distribution.
Large Vd implication
Large Vd implication
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Vd significance
Vd significance
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Hemodialysis toxicity
Hemodialysis toxicity
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Plasma Protein Binding
Plasma Protein Binding
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Albumin
Albumin
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Active Drug
Active Drug
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Displacement Effects
Displacement Effects
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Blood Brain Barrier
Blood Brain Barrier
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Placental Barrier
Placental Barrier
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Breast Milk
Breast Milk
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Redistribution of Drugs
Redistribution of Drugs
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Redistribution importance
Redistribution importance
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Liver role
Liver role
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Pro-Drug
Pro-Drug
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Study Notes
- Volume of body fluids at which the drug is distributed is termed volume of distribution.
Distribution
- Drugs are mainly distributed in body fluids.
- Plasma volume is 3L.
- Interstitial fluid volume is 9L.
- Intracellular fluid volume is 29L.
- Apparent Volume of distribution (Vd) is the volume of body fluids at which the drug is distributed.
Clinical Significance of Vd
- Used for estimation of site of drug distribution.
- Drugs with small Vd are confined to the vascular compartment with minimal tissue distribution.
- Drugs with large Vd has tissue distribution, specifically intracellularly.
- Used for calculation of total amount of drug in the body.
- Vd = total amount of drug/plasma conc.
- Another equation is V = total amount of drug/plasma conc.
- Hemodialysis is useful in cases of toxicity with drugs that have small Vd.
- Hemodialysis is has little significance in cases of drugs with large Vd.
Plasma Protein Binding
- Upon entering the blood, drugs may bind to plasma proteins.
- Albumin is the most important plasma protein that binds drugs.
- Hypoalbuminaemia, such as in starvation or malnutrition, can increase the free drug concentration, potentially changing a therapeutic dose to a toxic dose.
- Drugs bound to plasma proteins are not active since only the free part can produce a pharmacological effect.
- Drugs bound to plasma proteins are not diffusible, resulting in decreased distribution to tissues.
- Drugs bound to plasma proteins are not metabolized, leading to decreased uptake by liver cells and a prolonged effect.
- Drugs bound to plasma proteins are not excreted, causing decreased renal filtration and a prolonged effect.
- Warfarin, an oral anticoagulant, has high plasma protein binding at 99%.
- Only the free part of a drug is pharmacologically active, with warfarin having only 1% as such.
- Displacement of another 1% of a highly bound drug can lead to toxicity.
- Some drugs with high affinity for plasma protein binding, like Aspirin, can displace other drugs such as warfarin.
Distribution to Specialized Areas
- Passage across the blood-brain barrier (BBB): Non-ionized, highly lipid-soluble drugs can pass the BBB and affect the CNS.
- Passage to the fetus across the placental barrier: Non-ionized, lipid-soluble drugs can pass the placental barrier and affect the fetus.
- Drugs that pass the placental barrier may cause teratogenicity, such as phenytoin.
- Passage of drugs through breast milk: The pH of milk is more acidic than plasma, so basic drugs ionize and accumulate in the milk, which is called ion trapping.
- First-generation antihistamines can sedate a lactating baby, and morphine can make them addicted.
Redistribution of Drugs
- It can occur with highly lipid-soluble drugs like thiopental.
- Thiopental initially accumulates in the brain due to its high lipid solubility and the high blood flow to that organ.
- Thiopental then redistributes to poorly perfused adipose tissue. -Duration of some drugs as thiopental depend on rate of redistribution not rate of metabolism or excretion.
Biotransformation (Metabolism)
- Liver is the major site of drug metabolism.
- Other organs where drug metabolism occurs includes the kidney and lungs.
- Consequences of biotransformation include: 1. Active transforming to inactive (Inactivation of an active drug is most common). 2. Active transforming to production of active metabolites from active drugs. 3. Active transforming to production of toxic metabolite paracetamol. 4. Inactive transforming to active, Activation of an inactive drug (i.e pro-drug).
Extra questions
- Drugs that have volume of distribution more than 40 liters: Dialysis is not significant in case of toxicity.
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