Renal Drug Elimination Pathways Quiz

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Questions and Answers

Which one of the following is the primary elimination route for many medications?

Tubular reabsorption

Tubular secretion

Passive diffusion

Glomerular filtration (correct)

What process is usually responsible for the active secretion of drugs into the urine?

Passive diffusion

Tubular reabsorption

Glomerular filtration

Tubular secretion (correct)

What is the main factor that influences the process of tubular reabsorption?

Lipid solubility and degree of molecular ionization (correct)

Glomerular filtration rate

Tubular secretion rate

Molecular size

How does the glomerular filtration rate (GFR) typically change as humans age?

GFR decreases gradually with age Signup and view all the answers

Which of the following statements about tubular secretion is correct?

Tubular secretion is an active process conducted by relatively specific carriers or pumps Signup and view all the answers

What is the primary factor that determines the extent of tubular reabsorption?

Lipid solubility and degree of molecular ionization Signup and view all the answers

Which of the following equations describes the various routes of renal elimination?

$ ext{Renal elimination} = ext{Glomerular filtration} + ext{Tubular secretion} - ext{Tubular reabsorption}$ Signup and view all the answers

What is the typical range of glomerular filtration rate (GFR) in young, healthy adults between the ages of 18-22 years?

120-140 mL/min Signup and view all the answers

What is the expected glomerular filtration rate for otherwise healthy, normal 80-year-old adults?

~30–40 mL/min Signup and view all the answers

In patients with renal disease, what leads to the functional loss of nephrons?

Functional loss of nephrons Signup and view all the answers

What is the usual normal range for glomerular filtration rate according to most clinical laboratories?

~80–120 mL/min Signup and view all the answers

In acute renal failure, which of the following can lead to a sudden decrease in renal blood flow?

Hypovolemia Signup and view all the answers

What is the formula for calculating creatinine clearance rates as per the text?

(UCr ⋅ Vurine) / (SCr ⋅ T) Signup and view all the answers

Which type of patients are more likely to recover their kidney function to pre-insult level post-acute renal failure?

Patients with acute renal failure due to hypovolemia Signup and view all the answers

What happens to patients with chronic renal failure according to the text?

They experience irreversible damage Signup and view all the answers

How can creatinine clearance rates be measured according to the text?

By collecting urine for a specified period and collecting a blood sample for determination of serum creatinine at the midpoint of the concurrent urine collection time Signup and view all the answers

What is the body surface area used for normalizing estimated creatinine clearance?

1.73 m2 Signup and view all the answers

In a patient with renal dysfunction, what can be done to achieve a concentration/time profile similar to that seen in a normal patient receiving the normal dose?

Decrease the dose and lengthen the dosage interval Signup and view all the answers

What is the total daily dose for patients with renal disease receiving a dosage regimen of 150 mg every 6 hours?

600 mg/d Signup and view all the answers

For liver-metabolized drugs in patients with hepatic dysfunction, what dosing options are usually available?

Decreasing the dose and lengthening the dosage interval Signup and view all the answers

What effect does giving a smaller dose of a drug at the same dosage interval usually have on the concentration/time profile?

Lower peak steady-state concentration and higher trough steady-state concentration Signup and view all the answers

What happens to the concentration/time profile when giving the same dose but prolonging the dosage interval in a patient with renal disease?

Higher peak steady-state concentration and lower trough steady-state concentration Signup and view all the answers

What is the average steady-state concentration like when comparing renal disease dosage regimens?

Identical for both dosage schemes despite differences in peak and trough concentrations Signup and view all the answers

What type of drug metabolism reactions are often mediated by the cytochrome P-450 enzyme system (CYP)?

Phase I reactions Signup and view all the answers

Where is the cytochrome P-450 enzyme system (CYP) bound?

To the endoplasmic reticulum of hepatocytes Signup and view all the answers

What type of enzymes may mediate Phase II drug metabolism reactions in the liver?

Cytosolic enzymes contained in hepatocytes Signup and view all the answers

What is the general effect of Phase I and Phase II drug metabolism on the metabolites?

It makes the metabolites more water-soluble and less prone to elimination Signup and view all the answers

What is the primary function of transport proteins, such as P-glycoprotein, in the liver?

To actively secrete drug molecules into the bile Signup and view all the answers

What is the primary characteristic of hepatitis in patients?

Inflammation of the liver Signup and view all the answers

How does acute hepatitis affect drug metabolism in patients?

It causes a mild, transient decrease in drug metabolism that may require no or minor dosage changes Signup and view all the answers

What is the primary characteristic of hepatic cirrhosis in patients?

Permanent loss of functional hepatocytes Signup and view all the answers

What is the Child-Pugh score range that indicates a moderate decrease (approximately 25%) in initial daily drug dose for agents primarily metabolized by the liver?

8-9 Signup and view all the answers

If a drug is 95% liver metabolized with a usual dose of 500 mg every 6 hours, what would be an appropriate initial dose for a hepatic cirrhosis patient with a Child-Pugh score of 12?

Both a and b Signup and view all the answers

What is the Child-Pugh score range that indicates a significant decrease (approximately 50%) in initial daily dose for drugs that are mostly liver metabolized?

10 or greater Signup and view all the answers

If a patient has normal liver function, what is their Child-Pugh score?

5 Signup and view all the answers

What is the Child-Pugh score for a patient with grossly abnormal serum albumin, total bilirubin, prothrombin time values, severe ascites, and hepatic encephalopathy?

15 Signup and view all the answers

If a drug is primarily metabolized by the liver, what percentage of the initial daily dose would be appropriate for a patient with a Child-Pugh score of 8?

75% Signup and view all the answers

According to the information provided, which of the following statements is true?

Initial doses are meant as starting points for dosage titration based on patient response and avoidance of adverse effects. Signup and view all the answers

What is the total daily dose of a medication that is 95% liver metabolized with a usual dose of 500 mg every 6 hours?

2000 mg/day Signup and view all the answers

Study Notes

Renal Elimination

The primary elimination route for many medications is through the kidneys.
Active secretion of drugs into the urine is usually responsible for tubular secretion.
The main factor that influences tubular reabsorption is the lipid solubility of the drug.
The glomerular filtration rate (GFR) typically decreases with age.

Glomerular Filtration Rate (GFR)

The typical range of GFR in young, healthy adults is 95-145 mL/min.
The expected GFR for otherwise healthy, normal 80-year-old adults is 60-80 mL/min.
In patients with renal disease, the functional loss of nephrons leads to a decrease in GFR.
The usual normal range for GFR according to most clinical laboratories is 90-120 mL/min.

Renal Disease

Acute renal failure can lead to a sudden decrease in renal blood flow due to various factors.
In chronic renal failure, there is a gradual decline in kidney function over time.
Creatinine clearance rates can be measured using the formula: CrCl = (U x V) / (P x 1440).

Dosing Adjustments

In patients with renal disease, giving a smaller dose of a drug at the same dosage interval leads to a lower concentration/time profile.
Giving the same dose but prolonging the dosage interval in a patient with renal disease leads to a lower peak concentration and a longer elimination half-life.
The average steady-state concentration in renal disease dosage regimens is lower than in normal patients.
For liver-metabolized drugs in patients with hepatic dysfunction, dosing options include reducing the dose or increasing the dosage interval.

Hepatic Metabolism

The cytochrome P-450 enzyme system (CYP) is bound to the endoplasmic reticulum in the liver.
Cytochrome P-450 enzyme system (CYP) mediates Phase I drug metabolism reactions in the liver.
Phase II drug metabolism reactions in the liver are often mediated by enzymes such as glucuronidases and sulfotransferases.
The general effect of Phase I and Phase II drug metabolism on the metabolites is to increase their water solubility and facilitate excretion.

Hepatitis and Cirrhosis

The primary characteristic of hepatitis in patients is inflammation of the liver.
Acute hepatitis affects drug metabolism in patients by reducing the activity of hepatic enzymes.
The primary characteristic of hepatic cirrhosis in patients is scarring of the liver.
The Child-Pugh score indicates the severity of liver dysfunction, with higher scores indicating greater impairment.

Child-Pugh Score

A Child-Pugh score of 5-6 indicates normal liver function.
A Child-Pugh score of 7-9 indicates moderate liver dysfunction, and a score of 10-15 indicates severe liver dysfunction.
For drugs primarily metabolized by the liver, the initial daily dose is reduced by approximately 25% for patients with a Child-Pugh score of 7-9, and by approximately 50% for patients with a score of 10-15.

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Description

Test your knowledge on the renal elimination pathways of drugs, including glomerular filtration and tubular secretion in the kidneys. Learn about the primary routes through which medications are excreted from the body.