57 Questions
Which of the following best defines drug absorption?
The movement of the drug into the bloodstream after administration
What controls drug absorption?
Capillary walls and endothelial cells
Where does the exchange of materials between blood and cells primarily occur?
Capillaries
Which of the following types of capillaries has more pores allowing materials to move in/out?
Liver and kidney capillaries
What is the site of exchange of materials between blood and cells?
Capillary walls
How thick are capillary walls?
One cell thick
What allows ions, water, nutrients, and unbound drugs to move in/out of capillaries?
Pores in the capillary walls
Which pathway of drug excretion is the most important?
Renal (urine)
Under what condition will there be a greater intensity of drug effect?
Lower plasma protein, leading to increased unbound drug
What does the Volume Distribution Formula Vd= Amount of drug in the body/Plasma drug concentration represent?
Volume distribution of the drug in the body
Which drug excretion pathway involves enterohepatic cycling for some drugs?
GI (feces)
In what type of urine are acid drugs mostly ionized?
Alkaline urine
Which category of FDA Teratogenic Risk indicates absolute fetal abnormalities and not to be used at any time during pregnancy?
Category X
What is the effect on drug excretion during the first year of life in neonates/infants?
Reduced capacity for drug excretion
Which organ is primarily responsible for the excretion of general anesthetic gases?
Lungs
What happens to measures of renal function with age?
They are significantly reduced with age
What occurs to drug excretion after the first year of life in neonates/infants?
It gradually becomes proportional to those of the adult
Which factor does NOT influence the rate of drug absorption?
Gastrointestinal motility
In aging individuals, what contributes to decreased drug absorption?
Decreased intestinal surface area
Which organ is exposed to the largest amount of drug due to high blood flow?
Brain
What happens to water-soluble drugs in the body due to their solubility in water and plasma?
They are easily distributed throughout the body
How does aging affect drug binding to plasma proteins?
Reduces plasma protein levels
What does a lower percentage of body fat in neonates and infants result in regarding drug distribution?
Longer durations of action
What effect does a higher percentage of water in pediatrics have on drug concentrations?
Increases drug concentrations
What is the impact of high drug binding on drug distribution into tissues and metabolism?
Decreases distribution into tissues, decreases metabolism
What is the main function of the blood-brain barrier (BBB) in relation to drug absorption?
Allows passage of lipid-soluble drugs and smaller molecules into the brain
What is most influential in the rapid distribution of drugs into body tissues?
Blood flow to tissues with high blood flow
In drug excretion, which type of drugs are mostly ionized in alkaline urine?
Basic drugs
What is the primary pathway for the excretion of general anesthetic gases?
Respiratory excretion
During the first year of life, what happens to drug excretion in neonates/infants?
It slows down
What is the impact of high drug binding on drug distribution into tissues and metabolism?
Decreased distribution and metabolism
What is the category of FDA Teratogenic Risk that indicates absolute fetal abnormalities and prohibits use at any time during pregnancy?
Category X
How does aging affect measures of renal function such as GFR and creatinine clearance?
Decreases GFR and creatinine clearance
What occurs to water-soluble drugs in the body due to their solubility in water and plasma?
They are excreted in the feces
In what type of urine are acid drugs mostly ionized?
Acidic urine
What does the Volume Distribution Formula Vd= Amount of drug in the body/Plasma drug concentration represent?
The volume of distribution of the drug in body tissues
Which organ is exposed to the largest amount of drug due to high blood flow?
Liver
Which factor does NOT influence the rate of drug distribution?
Concentration gradient
What happens to water-soluble drugs in the body due to their solubility in water and plasma?
They are more easily distributed throughout the body
What is the effect of a higher percentage of water in pediatrics on drug concentrations?
Increased drug concentrations
How does aging affect drug binding to plasma proteins?
Decreases free drug available for distribution into tissues
What is most influential in the rapid distribution of drugs into body tissues?
Tissues with high blood flow
Where does the exchange of materials between blood and cells primarily occur?
Capillaries
What happens to drug excretion after the first year of life in neonates/infants?
Increases significantly
Which drug excretion pathway involves enterohepatic cycling for some drugs?
Biliary excretion
What does a lower percentage of body fat in neonates and infants result in regarding drug distribution?
Increased distribution to body tissues
What category of FDA Teratogenic Risk indicates absolute fetal abnormalities and not to be used at any time during pregnancy?
Category X
What is the primary site of exchange of materials between blood and cells?
Capillary walls
Which of the following barriers allows a large part of the basement membrane to be exposed, allowing large plasma proteins to pass through?
Capillary walls
What regulates drug absorption by controlling the movement of the drug into the bloodstream after administration?
Capillary walls
Which part of the body has capillary walls that are one cell thick, with pores allowing materials to move in and out?
Kidney
What is the role of capillaries in relation to drug absorption?
Movement of drugs into the bloodstream after administration
Which organ is exposed to the largest amount of drug due to high blood flow?
Liver
What controls drug absorption by regulating the movement of drugs into the bloodstream after administration?
Cell membrane
Which type of capillaries has more pores allowing materials to move in and out?
Sinusoidal capillaries
What allows ions, water, nutrients, and unbound drugs to move in/out of capillaries?
Pores in capillary walls
What is mainly responsible for controlling drug absorption by regulating the movement of drugs into the bloodstream after administration?
Cell membrane
Study Notes
-
Drug Absorption: Blood-Brain-Barrier (BBB) acts as a selective barrier for large hydrophilic molecules, only allowing passage of smaller, lipid-soluble drugs or through active transport.
-
To enter the brain, drugs must pass through endothelial cells or undergo active transport. Levodopa, a specific drug, is transported into the brain via a transporter.
-
The rate of drug absorption is influenced by factors such as:
- Surface area of absorption site
- Blood flow at absorption site
- Concentration gradient
- Drug formulations (sizes)
- Lipid solubility
- Un-ionized state
-
In neonates and infants:
- Smaller muscle mass results in slower absorption after IM injections
- Thinner skin allows for faster absorption of topically applied drugs
- Less acidic gastrointestinal tract
-
In aging individuals:
- Decreased intestinal surface area
- Decreased blood flow to the intestine
- Decreased gastrointestinal motility
- Decreased onset of action
- Decreased absorption of medications
-
Drug Distribution: After a drug gains access to the bloodstream, it is distributed to various tissues and organs of the body.
-
Factors affecting Drug Distribution:
- Blood flow: Tissues with high blood flow, such as the brain, liver, kidneys, and lungs, are exposed to the largest amount of drug.
- Blood-Brain Barrier: Brain composition of a large amount of lipid allows for lipid-soluble drugs to pass readily into the brain.
- Plasma Protein Binding: The distribution of drugs in the body is influenced by the percentage bound to plasma proteins. A higher percentage of binding reduces the free drug available for distribution into tissues.
- Distribution occurs most rapidly into tissues with high blood flow, such as "rich-vessel organs" (lungs, kidneys, liver, brain).
-
Water-soluble drugs vs. fat-soluble drugs:
- Water-soluble drugs are more easily distributed throughout the body due to their solubility in water and plasma.
- Fat-soluble drugs are stored in fatty tissues, acting as a drug reservoir, and are released into the bloodstream over a longer period of time.
-
Drug Binding:
- Drugs bound to plasma proteins are generally not pharmacologically active and have longer durations of action and low volumes of distribution.
- Aging reduces plasma protein levels, leading to increased free drug, decreased drug metabolism, and increased drug effect.
- Neonates and infants have a lower percentage of body fat, resulting in decreased distribution to body tissues and longer drug effects.
- Pediatrics have a higher percentage of water and are more easily dehydrated, leading to increased drug concentrations.
- High drug binding reduces the free drug available for distribution into tissues, decreases metabolism, and can be displaced by other drugs.
-
Drug Absorption: Blood-Brain-Barrier (BBB) acts as a selective barrier for large hydrophilic molecules, only allowing passage of smaller, lipid-soluble drugs or through active transport.
-
To enter the brain, drugs must pass through endothelial cells or undergo active transport. Levodopa, a specific drug, is transported into the brain via a transporter.
-
The rate of drug absorption is influenced by factors such as:
- Surface area of absorption site
- Blood flow at absorption site
- Concentration gradient
- Drug formulations (sizes)
- Lipid solubility
- Un-ionized state
-
In neonates and infants:
- Smaller muscle mass results in slower absorption after IM injections
- Thinner skin allows for faster absorption of topically applied drugs
- Less acidic gastrointestinal tract
-
In aging individuals:
- Decreased intestinal surface area
- Decreased blood flow to the intestine
- Decreased gastrointestinal motility
- Decreased onset of action
- Decreased absorption of medications
-
Drug Distribution: After a drug gains access to the bloodstream, it is distributed to various tissues and organs of the body.
-
Factors affecting Drug Distribution:
- Blood flow: Tissues with high blood flow, such as the brain, liver, kidneys, and lungs, are exposed to the largest amount of drug.
- Blood-Brain Barrier: Brain composition of a large amount of lipid allows for lipid-soluble drugs to pass readily into the brain.
- Plasma Protein Binding: The distribution of drugs in the body is influenced by the percentage bound to plasma proteins. A higher percentage of binding reduces the free drug available for distribution into tissues.
- Distribution occurs most rapidly into tissues with high blood flow, such as "rich-vessel organs" (lungs, kidneys, liver, brain).
-
Water-soluble drugs vs. fat-soluble drugs:
- Water-soluble drugs are more easily distributed throughout the body due to their solubility in water and plasma.
- Fat-soluble drugs are stored in fatty tissues, acting as a drug reservoir, and are released into the bloodstream over a longer period of time.
-
Drug Binding:
- Drugs bound to plasma proteins are generally not pharmacologically active and have longer durations of action and low volumes of distribution.
- Aging reduces plasma protein levels, leading to increased free drug, decreased drug metabolism, and increased drug effect.
- Neonates and infants have a lower percentage of body fat, resulting in decreased distribution to body tissues and longer drug effects.
- Pediatrics have a higher percentage of water and are more easily dehydrated, leading to increased drug concentrations.
- High drug binding reduces the free drug available for distribution into tissues, decreases metabolism, and can be displaced by other drugs.
Test your knowledge of drug absorption, distribution, and excretion with this quiz based on the fundamentals of pharmacology lecture by Hoang Nguyen, M.D., Ph.D., RPh., FACHE. Assess your understanding of mechanisms and learning objectives related to pharmacokinetics.
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