Pharma - Berto - L3 part 2

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Questions and Answers

What best describes local action of a drug?

The action is systemic and affects all organ systems.

The action is felt throughout the entire body.

The action is transmitted to a linked nervous system area.

The action is only manifested at the site of application. (correct)

Which of the following processes is NOT part of the pharmacokinetics acronym ADME?

Absorption

Metabolism

Expenditure (correct)

Distribution

What is the primary focus of pharmacokinetics?

The temporal concentration trend of a drug in the body. (correct)

The effects of a drug at the cellular level.

The psychological effects of drug consumption.

The study of drug interactions.

Which of the following terms refers to the process by which a drug moves from the blood to tissues?

Distribution Signup and view all the answers

Why is it important for patients to follow the therapeutic regimen?

To maintain optimal drug concentration in the site of action. Signup and view all the answers

What type of action extends to a whole area connected at nervous and vascular levels?

Regional action Signup and view all the answers

What is the overall goal of pharmacokinetics?

To formulate precise rules to optimize therapy. Signup and view all the answers

What must occur before a drug can exert its effect in the body?

It must first be absorbed into the systemic circulation. Signup and view all the answers

Which concentration is critical in determining the therapeutic regimen?

Minimum efficacy concentration Signup and view all the answers

How does metabolism affect a drug within pharmacokinetics?

It prepares the drug for elimination from the body. Signup and view all the answers

What characterizes zero-order kinetics in drug transport?

The transfer occurs at a constant velocity regardless of concentration. Signup and view all the answers

What happens when the partition coefficient (PC) of a drug is much larger than 1?

The drug may accumulate excessively in the double layer of the membrane. Signup and view all the answers

In which scenario does first-order kinetics occur during drug transport?

When the drug is present in low concentration compared to transport systems. Signup and view all the answers

Which of the following factors does NOT influence the flow of a drug across a membrane according to Fick’s Law?

Temperature of the environment. Signup and view all the answers

What process involves the formation of vesicles for large, hydrophilic drugs?

Endocytosis Signup and view all the answers

How does passive diffusion of a drug proceed?

The velocity decreases as concentration differences equalize. Signup and view all the answers

Which factors influence the permeability of membranes for drug absorption?

Thickness, area of barrier, and vascular permeability. Signup and view all the answers

Under what condition can a weak acid like acetylsalicylic acid more easily diffuse through a membrane?

At lower pH levels. Signup and view all the answers

How does binding to plasma proteins affect the penetration of drugs through membranes?

Only the free portion can pass through membranes. Signup and view all the answers

What is a characteristic of transcytosis in cellular transport?

It releases vesicle contents on the opposite side of the cell. Signup and view all the answers

What happens to a weak base when it is placed in an acidic bodily fluid?

It gets ionized and cannot diffuse across the membrane. Signup and view all the answers

What typically occurs when the drug concentration is greater than the saturated transporter capacity?

The velocity of transport becomes constant. Signup and view all the answers

Which of the following best represents a characteristic necessary for a drug to effectively cross the membrane?

A balance of lipophilicity and hydrophilicity. Signup and view all the answers

Which transport mechanism always follows the concentration gradient and does not require energy?

Facilitated transport. Signup and view all the answers

Which of the following is the least permissive barrier for drug absorption?

Blood-Brain Barrier Signup and view all the answers

What happens during receptor-mediated endocytosis?

After binding, receptors can aggregate and be recycled. Signup and view all the answers

In relation to drug concentration, what determines the crossing velocity from compartment 1 to compartment 2?

The difference in concentration between the two compartments. Signup and view all the answers

What term describes the build-up of a higher concentration of a chemical across a cell membrane due to pH differences?

Ion trapping. Signup and view all the answers

What is the primary reason the blood-brain barrier (BBB) is highly impermeable?

To protect the CNS from toxic substances Signup and view all the answers

Which area of the body has a more permeable barrier compared to the normal BBB?

Chemoreceptor trigger zone (CTZ) Signup and view all the answers

What is one of the main disadvantages of the oral administration route?

It limits the amount of drug reaching the systemic circulation Signup and view all the answers

Which factor directly influences the bioavailability of a drug administered orally?

The concentration gradient of the drug Signup and view all the answers

What is first-pass metabolism?

The initial metabolic process a drug undergoes before entering systemic circulation Signup and view all the answers

What is the primary site of drug absorption when taken orally?

Small intestine Signup and view all the answers

What is the effect of carbohydrates on blood flow during drug absorption?

They decrease blood flow Signup and view all the answers

How does the presence of food generally affect drug absorption after oral administration?

It may increase or decrease absorption depending on the type of food Signup and view all the answers

What does selectivity refer to regarding a drug's interaction with receptors?

A drug's capability to recognize one receptor subtype among many Signup and view all the answers

Which factor is NOT important for oral bioavailability?

Expiration date of the drug Signup and view all the answers

Study Notes

Drug Action Types

Local Action: Effects confined to the application site (e.g., local anesthetics, topical anti-inflammatories).
Regional Action: Effects extend to the entire area connected via the nervous and vascular systems (e.g., epidural anesthesia).
Systemic Action: Drug affects the whole organism via systemic circulation.

Pharmacokinetics Overview

Definition: Study of drug concentration trends over time in the body.
Processes Involved:
- Absorption: Drug movement from administration site to bloodstream.
- Distribution: Drug movement from blood to tissues.
- Metabolism: Biotransformation processes that inactivate drugs for elimination.
- Excretion: Elimination of drugs from the body.
Goal: Optimize therapy by predicting drug concentration at action sites.

Membrane Crossing Mechanisms

Drug Crossing Mechanisms:
- Passive Diffusion: Drug moves along concentration gradients without energy.
- Transport Mediated: Channels and carriers facilitate drug movement.
- Endocytosis/Exocytosis: Vesicle formation for large, hydrophilic drugs.

Partition Coefficient (PC)

Definition: Ratio of drug concentration in oil vs. water; indicates lipophilicity.
PC Interpretation:
- PC > 1: Compound is lipophilic; easy membrane diffusion.
- PC close to 0: Compound is hydrophilic; difficult to cross membranes.
Factors Affecting PC: Metabolism, pH, and pKa of drug.

Henderson-Hasselbalch Equation

Purpose: Determines the permeability of charged molecules across membranes.
Ion Trapping: Weak acids/bases can become charged in different pH environments, affecting their permeability.

Fick's Law

Principles:
- Drug crossing is favored by PC near 1.
- Thinner membranes enhance diffusion; larger surfaces favor it.
- Flow is affected by concentration differences across compartments.

Kinetics of Drug Transport

Passive Diffusion Kinetics: Follows first-order kinetics where diffusion rate decreases until equilibrium.
Active Transport: Involves zero-order kinetics at saturation; constant velocity regardless of concentration.

Administration Routes

Enteral: Oral, sublingual, rectal routes; drugs pass through gastrointestinal tract.
Parenteral: Intravascular (IV), intramuscular, cutaneous, and other routes bypass GI tract.

Oral Administration

Key Steps for Oral Drugs:
- Must dissolve in the digestive tract.
- Cross gastrointestinal mucosa to enter portal circulation, bypassing hepatic filtering.
Bioavailability Factors: Solubility, surface area, vascularization, and organ functional state influence how much drug reaches systemic circulation.

Blood-Brain Barrier (BBB)

Characteristics: Highly impermeable due to tight junctions and astrocyte end-feet.
Factors Affecting Drug Passage:
- Binding to plasma proteins.
- Ionization: Only non-ionized drugs can cross.
- Lipophilicity: Highly lipophilic drugs penetrate better.
Transport Mechanisms: Specialized transporters aid larger molecules' crossing.

Specific Flow and Permeability

Specific Flow: Indicates membrane permeability; higher specific flow accelerates absorption.
Barrier Features: Vascular permeability varies by tissue type; highly vascular areas may still be impermeable.

Key Definitions

Selectivity: Ability of a drug to bind preferentially to one receptor subtype over others.
Specificity: Degree to which a drug interacts with a particular receptor.

Conclusion

Understanding pharmacokinetics, membrane dynamics, and administration routes is crucial for drug efficacy and patient therapy optimization.

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Description

This quiz covers the different types of drug actions based on their effects on the body. Learn about local, regional, and systemic actions, and how these classifications influence medical treatment strategies. Ideal for students in pharmacology or medicine.