10 Questions
Which enzyme does grapefruit juice inhibit, along with other fruit juices?
OATP1A2
Which of the following drugs does grapefruit juice NOT increase the oral bioavailability of?
Felodipine
Which type of vessels surround the small intestine and take up drugs from the basolateral side of the intestinal membrane?
Mesenteric vessels
Which juice has a greater effect on oral bioavailability when compared to regular-strength juice?
Double-strength juice
Which of the following drugs has NOT shown large increases in plasma concentrations when taken with grapefruit juice?
Cyclosporine
Which two factors need to be considered when discussing drug distribution?
How rapidly and to what extent the drug is absorbed
How can information about the rate of drug distribution be obtained?
By observing the changes in plasma concentrations in the early period after drug administration
Why is it rarely possible to measure tissue concentrations of a drug clinically?
Because it is difficult to access tissues for measurement
What does the plasma concentration of a drug represent in terms of drug distribution?
The extent of drug distribution
What does the plasma concentration of a drug constitute in terms of drug distribution?
A window for observation
Study Notes
Enzyme Inhibition and Grapefruit Juice
- CYP3A4 enzyme is inhibited by grapefruit juice, along with other fruit juices.
Drug Bioavailability
- Grapefruit juice does NOT increase the oral bioavailability of Pravastatin.
Intestinal Absorption
- Lymphatic vessels surround the small intestine and take up drugs from the basolateral side of the intestinal membrane.
Comparative Effects of Juices on Oral Bioavailability
- High-strength juice has a greater effect on oral bioavailability when compared to regular-strength juice.
Drug Interactions with Grapefruit Juice
- Fexofenadine has NOT shown large increases in plasma concentrations when taken with grapefruit juice.
Factors Affecting Drug Distribution
- Two factors to consider when discussing drug distribution are:
- Plasma protein binding
- Tissue permeability
Obtaining Information on Drug Distribution
- Information about the rate of drug distribution can be obtained through pharmacokinetic studies.
Limitations of Measuring Tissue Concentrations
- It is rarely possible to measure tissue concentrations of a drug clinically due to ethical and logistical reasons.
Plasma Concentration and Drug Distribution
- The plasma concentration of a drug represents the amount of drug in the bloodstream at a given time.
- The plasma concentration of a drug constitutes the central compartment in pharmacokinetic models.
Test your knowledge on drug administration, absorption, and bioavailability with this quiz. Learn about the impact of grapefruit juice on drug absorption and the role of intestinal CYP3A4. Discover how grapefruit juice affects the oral bioavailability of certain drugs.
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