Pharma - Berto - L6 part 1

Questions and Answers

What characterizes the glomerular filtration phase of renal elimination?

It primarily removes highly charged drugs from the plasma.

It filters a large volume of plasma without selectivity. (correct)

It selectively filters lipophilic drugs preferentially.

It is highly selective for drugs bound to plasma proteins.

Which statement is true about the renal excretion process?

Passive tubular reabsorption occurs after active tubular secretion. (correct)

99% of the volume filtered in glomerular filtration is secreted in urine.

Drugs bound to plasma proteins are easily filtered by the glomeruli.

Active tubular secretion occurs before glomerular filtration.

What is the primary route of elimination for most drugs?

Pulmonary route is the main excretion pathway.

Renal route is predominantly used for water-soluble drugs. (correct)

Hepatic route is preferred for all drugs.

Accessory routes are the primary elimination methods.

Which of the following statements is false regarding the hepatic route of elimination?

It filters substances based on their lipophilicity. Signup and view all the answers

How does lipophilicity affect the reabsorption of drugs during renal elimination?

Reabsorption is directly proportional to lipophilicity. Signup and view all the answers

Which accessory route of drug elimination is specifically crucial for breastfeeding women?

Milk Signup and view all the answers

Which of the following is not a characteristic of glomerular filtration?

It allows passage of drugs bound to plasma proteins. Signup and view all the answers

What is the main driving force for the filtration process occurring in the glomerulus?

Blood hydrostatic pressure Signup and view all the answers

What is the role of the pulmonary route in drug elimination?

It is significant for inhaled drugs and volatile substances. Signup and view all the answers

Which condition would increase the excretion of weak acids like barbituric acid?

Increasing urine pH Signup and view all the answers

During renal elimination, which condition would most likely lead to minimal reabsorption?

Highly hydrophilic and charged drugs. Signup and view all the answers

Which statement about tubular secretion in the nephron is correct?

It includes systems specifically for organic cations and anions. Signup and view all the answers

How does entero-hepatic circulation impact drug elimination?

It allows drugs to remain active longer in the organism. Signup and view all the answers

Which process is primarily responsible for the large volume of plasma reabsorption after glomerular filtration?

Passive tubular reabsorption Signup and view all the answers

The clearance of a drug primarily indicates what?

The body's ability to eliminate the drug over time. Signup and view all the answers

What role does the conjugation phase play in drug metabolism?

It forms hydrophilic compounds for easier excretion. Signup and view all the answers

Which of the following statements is true regarding the excretion rate and elimination kinetics?

Elimination is a constant fraction of the drug per unit of time. Signup and view all the answers

In which part of the nephron does active reabsorption of anions occur?

Distal convoluted tubule Signup and view all the answers

What is the importance of the concept of organ clearance?

It helps predict the accumulation of drugs in the body. Signup and view all the answers

Which of the following describes the main characteristic of tubular reabsorption?

It can favor the excretion of specific drugs through urine manipulation. Signup and view all the answers

What is the renal clearance rate for a free drug that is not reabsorbed nor secreted?

130 ml/min Signup and view all the answers

How does increased renal clearance affect the half-life of a drug?

It decreases the half-life. Signup and view all the answers

What condition might result in a total reabsorption of creatinine, leading to a clearance value of zero?

Kidney dysfunction Signup and view all the answers

What happens to drug elimination when its plasma concentration exceeds a certain threshold?

Elimination switches to zero-order kinetics. Signup and view all the answers

What does the Area Under the Curve (AUC) represent in pharmacokinetics?

The total drug absorbed into circulation. Signup and view all the answers

Which parameter is directly proportional to the half-life of a drug?

Volume distribution (Vd) Signup and view all the answers

How can a doctor estimate the glomerular filtration rate (GFR)?

By analyzing blood creatinine levels combined with patient demographics. Signup and view all the answers

What characterizes a single compartment pharmacokinetic model?

Drug concentration increases rapidly and then stabilizes. Signup and view all the answers

What is the expected AUC if a drug is administered at dose D with 100% bioavailability?

D/Cl Signup and view all the answers

What effect does a slow absorption formulation have on drug plasma concentration?

It delays the peak concentration but maintains it longer. Signup and view all the answers

Study Notes

Elimination Phase in Pharmacokinetics

The elimination phase is the final stage of pharmacokinetics, involving drug excretion processes.
Main routes of elimination: renal (kidneys), hepatic (liver), pulmonary (lungs).
Accessory routes include saliva, sweat, tears, milk, hair, and skin.

Renal Elimination

Renal elimination is the primary route, primarily for water-soluble substances.
Involves three main processes: glomerular filtration, active tubular secretion, and passive tubular reabsorption.

Glomerular Filtration

Characterized by a large volume of plasma filtered by the glomeruli.
Plasma-bound drugs cannot be filtered; only free drugs are later reabsorbed.
Filtration is driven by blood hydrostatic pressure; important substances like proteins and blood cells are retained in circulation.

Tubular Reabsorption

A passive diffusion mechanism influenced by urinary pH; affects the excretion of weak acids and bases.
Weak acids are reabsorbed in acidic urine, while weak bases are favored in basic urine.
Ionized molecules are excreted, allowing manipulation of urine pH to enhance drug elimination.

Tubular Secretion

An active process involving two transport systems: one for organic anions (e.g., diuretics, NSAIDs) and one for organic cations (e.g., morphine).
Both systems can be subject to competition and saturation, affecting secretion efficacy.

Hepatic-Biliary Excretion

Drugs can be metabolized in the liver and excreted via bile.
Biliary excretion is influenced by drug polarity and molecular weight; larger, hydrophilic substances are targeted.
Entero-hepatic circulation prolongs drug activity by recycling some substances back into circulation.

Elimination Kinetics

Drug elimination typically follows first-order kinetics: a constant fraction of the drug is eliminated over time.
Ke (elimination rate constant) indicates the elimination velocity; inversely related to half-life.
Total clearance (Cl) relates clearance rates of various organs responsible for drug excretion.

Clearance

The rate at which a drug is removed from the plasma, measured in ml/min or L/hr.
Renal clearance reflects kidney function: 20% filtration rate (~130 ml/min) in healthy individuals.
Increased creatinine levels indicate reduced renal clearance, affecting drug half-life.

Half-Life

The half-life of a drug is the time required for plasma concentration to reduce by half.
Influenced by clearance (inversely) and volume of distribution (directly).
Abnormalities in organ function lead to increased half-life and extended therapeutic effects.

AUC (Area Under the Curve)

Represents drug bioavailability; correlates with the amount of unchanged drug reaching circulation.
AUC can be calculated to assess total plasma concentration and elimination rate.
Understanding absorption and elimination speeds helps optimize drug dosing for therapeutic efficacy.

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Description

Explore the elimination phase in pharmacokinetics, focusing on the routes and processes involved in drug excretion. Learn about renal elimination, glomerular filtration, and tubular reabsorption in detail.