Pharma - Berto - L4 part 2

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Questions and Answers

What happens to the drug concentration at the action site in the presence of massive binding to plasma proteins?

It is much lower than in the plasma. (correct)

It is higher than in the plasma.

It remains the same as in the plasma.

It fluctuates based on the dosage.

Which effect does the massive binding of drugs to plasma proteins NOT have?

Limits glomerular filtration of the drug.

Increases the elimination of the drug. (correct)

Slows down the plasma concentration of free drugs.

Limits the drug concentration at the action site.

Which of the following can displace bilirubin from plasma proteins, leading to possible toxicity?

Tetracyclines

Chloroquine

Digoxin

Sulfonamides (correct)

In which specific tissue does digoxin tend to accumulate?

Heart and muscles Signup and view all the answers

How does the age of a patient affect the binding capacity of drugs to plasma proteins?

Newborns have less albumin, resulting in higher free drug levels. Signup and view all the answers

What pathological condition can lead to a decrease in albumin levels?

Chronic liver disease Signup and view all the answers

What primarily influences the absorption phase of a drug?

The route of administration Signup and view all the answers

How does the peak blood concentration of a drug administered orally compare to that of an intravenous administration?

The peak is delayed and lower with oral administration. Signup and view all the answers

What occurs after the peak concentration in oral drug administration?

The absorption phase continues slowly, keeping concentration higher. Signup and view all the answers

What factor does NOT influence the distribution of a drug in the body?

The presence of food in the gastrointestinal tract Signup and view all the answers

What is the major water compartment involved in drug distribution?

Intracellular fluid Signup and view all the answers

Which administration route typically results in the fastest absorption phase for a drug?

Intravenous administration Signup and view all the answers

Which statement regarding the elimination curve of different administration routes is correct?

It remains constant regardless of the administration route. Signup and view all the answers

How does body water composition affect drug distribution?

Variations in body water can change the volume of distribution. Signup and view all the answers

What is the approximate percentage of body weight that is made up of plasma?

4% Signup and view all the answers

Which factor primarily affects the speed of drug distribution to tissues?

Perfusion rate of the tissue Signup and view all the answers

What is the consequence of a drug accumulating in tissue compartments?

It may lead to toxicity. Signup and view all the answers

What does the apparent volume of distribution (Vd) represent?

A theoretical volume needed to dissolve a drug at a specific concentration Signup and view all the answers

Which tissue has the highest capillary permeability?

Liver Signup and view all the answers

How does the partition coefficient affect drug distribution?

It reflects the drug's ability to cross biological membranes. Signup and view all the answers

What characterizes highly lipophilic drugs regarding their distribution?

They quickly equilibrate with highly perfused tissues. Signup and view all the answers

Which of the following factors is NOT involved in the drug's ability to bind to plasma proteins?

Size of the plasma protein molecules Signup and view all the answers

What happens when a drug has a Kp greater than 1?

The drug accumulates significantly in tissues. Signup and view all the answers

Which protein predominantly binds organic anions in plasma?

Albumin Signup and view all the answers

What is the impact of an increase in plasma binding sites on the bound fraction of a drug?

It increases the bound fraction of the drug. Signup and view all the answers

Study Notes

Absorption

Route of administration significantly influences drug absorption.
Graphs illustrate plasma concentration over time, comprised of elimination (red) and absorption (green) curves.
Elimination kinetics remain constant regardless of administration route; absorption kinetics vary.
Oral administration shows a delayed peak concentration, lower than intravenous (IV), but maintains higher post-peak levels due to ongoing absorption.
Intramuscular administration reflects a trend between oral and IV routes.
Rapid absorption occurs with IV bolus; quick onset into bloodstream followed by prolonged elimination phase.

Distribution

Drug distribution facilitates transfer between various body compartments, primarily between blood and water compartments.
Body water composition: 60% of body weight; decreases with age and is lower in females.
Major water compartments: plasma (4%), extracellular fluid (16%), intracellular fluid (40%).
Distribution rate affected by drug concentration in plasma, blood flow, compartment volume, membrane permeability, and protein binding.
Distribution phases:
- 1st phase: rapid distribution to highly perfused tissues (lungs, kidneys, liver, heart, brain).
- 2nd phase: slower distribution to less perfused tissues.
- 3rd phase: redistribution of the drug.
High lipophilicity facilitates quick blood-brain barrier (BBB) crossing and CNS access.

Capillary Permeability

Capillary permeability varies by tissue type: liver > renal glomeruli > muscle > brain.
Liver capillaries allow for significant permeability; brain capillaries limit the passage of water-soluble molecules.
Only free drug molecules can exit blood vessels to exert therapeutic effects; bound drugs remain ineffective.

Apparent Volume of Distribution (Vd)

Vd represents the theoretical volume required to dissolve a drug to achieve plasma concentration.
Relationship defined as Vd = D/Cp; influenced by drug's lipophilicity and protein binding.
When Kp (tissue-to-plasma concentration ratio) exceeds one, apparent volume surpasses real volume, indicating potential accumulation in tissues.

Binding to Plasma Proteins

Drugs bind to plasma proteins like albumin (50% of plasma proteins) and alpha-1-acid glycoprotein (AGP).
Only unbound fractions exert therapeutic effects; binding limits distribution and elimination.
High binding can lead to lower apparent volumes and potential toxicity due to restricted availability at action sites.
Factors impacting plasma protein concentration:
- Physiological (age, liver health)
- Pathological (chronic diseases, inflammatory states)
- Genetic and environmental influences.

Clinical Implications

Free drug concentration is crucial for therapeutic efficacy; high binding restricts action and can prolong half-life.
Displacement effects: newer drugs can displace others, increasing free concentrations and risk of toxicity.
Specific tissues can act as drug depots, leading to potential toxicity: liver (tetracyclines), heart/muscle (digoxin), adipose tissue (thiopental), bone (heavy metals).

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Description

This quiz explores the relationship between drug administration routes and their impact on absorption kinetics. By examining plasma concentration curves, participants will analyze how different routes affect absorption, while noting that elimination kinetics remain unchanged. Dive into the concepts of pharmacokinetics and understand the underlying principles.