47 Questions
What is the advantage of using extended-release tablets for oral morphine?
Reduced frequency of administration
What are the advantages of sublingual and buccal routes of drug absorption?
Rapid absorption
When is parenteral drug administration used?
For drugs requiring rapid onset of action
What are the benefits of parenteral routes of drug administration?
High bioavailability
What is the formula for calculating the volume of distribution (Vd)?
Vd = C0
In which compartment of the body is a drug effectively trapped if it has a high molecular weight or is extensively protein bound?
Plasma compartment
Which type of drug distribution results in a low volume of distribution (Vd) that approximates the plasma volume?
Distribution into plasma compartment
What does a low volume of distribution (Vd) indicate about the distribution of a drug in the body?
Trapping within the plasma compartment
What is the energy source driving active transport of drugs across the cell membrane?
Hydrolysis of adenosine triphosphate (ATP)
Which mechanism of drug absorption involves specific carrier proteins that span the cell membrane?
Active transport
What type of absorption is used to transport drugs of exceptionally large size across the cell membrane?
Endocytosis
Which process involves cells using vesicle formation to secrete substances out of the cell?
Exocytosis
Which process involves drugs entering the kidney through renal arteries?
Glomerular filtration
What is the normal glomerular filtration rate (GFR)?
125 mL/min
What influences the passage of drugs into the glomerular filtrate?
Variations in GFR and protein binding of drugs
Where do drugs that were not transferred into the glomerular filtrate leave the glomeruli?
Efferent arterioles
What factor strongly influences the distribution of lipophilic drugs?
Blood flow to the area
Which type of drug distribution may serve as a major source of the drug and prolong its actions or cause local drug toxicity?
Binding to tissue proteins
What is the apparent volume of distribution (Vd) defined as?
The fluid volume required to contain the entire drug in the body at the same concentration measured in the plasma
In drug distribution, drugs that accumulate in tissues may do so due to:
Binding to lipids, proteins, or nucleic acids
In which clinical situation may a patient require a decrease in drug dosage or less frequent dosing?
Decreased metabolism due to a concomitant drug inhibiting metabolism
Which abnormality is likely to result in an increase in drug half-life for a patient?
Decreased metabolism due to hepatic insufficiency as with cirrhosis
What can result in the necessity of higher doses or more frequent dosing intervals for a drug?
Increased hepatic blood flow
What factors influence the distribution of a drug from the plasma to the interstitium?
Blood flow, capillary permeability, tissue volume, binding of the drug to plasma and tissue proteins, and relative lipophilicity of the drug
Why does propofol rapidly distribute into the central nervous system (CNS) when administered intravenously?
High blood flow and high lipophilicity of propofol
What determines capillary permeability in the process of drug distribution?
Capillary structure and chemical nature of the drug
Which factor partly explains the short duration of hypnosis produced by an IV bolus of propofol?
Variation in blood flow to tissue capillaries
What does the volume of distribution (Vd) indicate about a drug that has a low Vd?
The drug has a low Vd that approximates the plasma volume
In which compartment of the body would a drug with a low molecular weight but is hydrophilic distribute into?
Interstitial fluid
What factor could lead to a drug having a high volume of distribution (Vd)?
Extensive protein binding and high molecular weight
What does the volume of distribution (Vd) compare the distribution of a drug with?
Volumes of the water compartments in the body
Why is the rectal route of drug administration advantageous in preventing drug destruction in the gastrointestinal (GI) environment?
Because it bypasses the portal circulation and minimizes biotransformation by the liver
What is a significant disadvantage of the rectal route of drug administration?
Erratic and incomplete absorption of drugs
How does the rate and extent of drug absorption vary for routes of administration other than intravenous?
They result in lower bioavailability due to incomplete absorption
What does the absorption of drugs involve?
Transfer of a drug from the site of administration to the bloodstream
What type of distribution does aminoglycoside antibiotics exhibit?
Distribution into the extracellular fluid
What does a larger volume of distribution (Vd) generally indicate?
Greater distribution into tissues
How is the apparent Vd defined?
Volume of drug distributed into the extracellular fluid
What allows for the calculation of Vd in drug clearance?
First order drug elimination
Which type of drug kinetics is most commonly observed for drug elimination?
First-order kinetics
What allows the kidney to efficiently eliminate lipophilic drugs?
Increased polarity due to metabolism
Which general set of reactions in the liver leads to the conversion of lipid-soluble agents into more polar substances?
Phase I and phase II reactions
What must drugs be sufficiently polar to be, in order to be eliminated from the body?
Eliminated through urinary excretion
What are the factors that influence the distribution of a drug from the plasma to the interstitium?
All of the above
Why does propofol rapidly distribute into the central nervous system (CNS) when administered intravenously?
High blood flow and high lipophilicity
What may partly explain the short duration of hypnosis produced by an IV bolus of propofol?
Low blood flow to skeletal muscles
What determines capillary permeability in the process of drug distribution?
Capillary structure and chemical nature of the drug
Test your knowledge about the concept of volume of distribution in pharmacokinetics. Understand how it is calculated and its significance in comparing the distribution of a drug with the volumes of water compartments in the body.
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