Metabolism and Excretion Quiz

Questions and Answers

What is the primary purpose of drug metabolism in the body?

To facilitate excretion of drugs and reduce toxicity (correct)

To enhance the lipophilicity of drugs for better absorption

To convert inactive drugs into active forms

To increase the therapeutic effect of active drugs

In which cellular organelle does the Phase 1 reaction of drug metabolism predominantly take place?

Smooth endoplasmic reticulum and mitochondria (correct)

Golgi apparatus

Nucleus

Ribosomes

Which factor primarily affects the metabolism rate of drugs in individuals?

Body mass index

Genetic polymorphism of drug metabolizing enzymes (correct)

Age of the patient

Recent food intake

What effect do CYP450 inducers have on the metabolism of coadministered drugs?

They enhance the metabolic breakdown of drugs, reducing therapeutic effects Signup and view all the answers

How does liver disease, such as cirrhosis, affect drug metabolism?

It decreases both the amount and efficacy of CYP450 enzymes Signup and view all the answers

Which phase of drug metabolism primarily increases polarity and water solubility of substances?

Phase 2 Reaction Signup and view all the answers

Which of the following factors does NOT affect drug elimination or clearance?

Intravenous injection speed Signup and view all the answers

What is primarily responsible for the filtration of drugs at the renal glomerulus?

Hydrostatic pressure Signup and view all the answers

Which transport mechanism is primarily utilized for the secretion of polar, water-soluble drugs in the kidneys?

Active transport via organic ion transporters Signup and view all the answers

Which transferase enzyme is responsible for methylation in drug metabolism?

Methyltransferase Signup and view all the answers

Which condition would likely result in decreased drug-protein binding and increased serum concentration of free drugs?

Liver cirrhosis Signup and view all the answers

How does the lipophilicity of a drug influence its protein binding?

Higher lipophilicity results in increased protein binding Signup and view all the answers

Which method is NOT a primary route for drug excretion from the body?

Sweat excretion through the skin Signup and view all the answers

Study Notes

Metabolism

Drug metabolism involves converting active drugs into inactive forms to facilitate elimination and reduce toxicity.
Prodrugs are inactive compounds transformed into active drugs through metabolism.
The liver serves as the primary site for drug metabolism.

Drug Metabolism Phases

Phase 1 Reactions:
- Involve intramolecular modifications via oxidation, reduction, and hydrolysis.
- Enzyme systems include the CYP450 family, with CYP3A4 metabolizing 50% of all drugs.
- Converts lipophilic compounds into more polar, water-soluble forms aiding in excretion.
- Genetic polymorphism affects drug metabolism, particularly with CYP2D6.
- Rapid metabolizers convert drugs quickly, reducing therapeutic effects; slow metabolizers risk toxicity from increased active drug levels.
Phase 2 Reactions:
- Focus on conjugation, further increasing polarity and water solubility.
- Enzymes involved include transferases such as methyltransferase and glucuronosyltransferases (most common).

Factors Influencing Metabolism

CYP450 Inducers: Increase enzyme activity leading to decreased therapeutic effects of coadministered drugs.
CYP450 Inhibitors: Decrease enzyme activity resulting in increased side effects and toxicity.
Liver diseases like cirrhosis decrease CYP450 activity, raising blood levels of active drugs.
Age can also influence drug metabolism efficiency.

Excretion

Primary excretion pathway is through the kidneys, but drugs can also be eliminated via bile, exhalation, and feces.
Filtration:
- Involves glomerular filtration rate (GFR) influenced by renal disease and hydrostatic pressure.
- Drug-protein binding significantly impacts filtration rates; increased binding leads to lower filtration and higher serum drug concentrations.

Secretion

Active transport from peritubular capillaries to the tubular lumen, primarily for polar and water-soluble drugs.
Passive diffusion applies to nonpolar and lipid-soluble drugs due to concentration gradients.

Reabsorption

Occurs mainly in the distal convoluted tubule.
Nonpolar, lipid-soluble substances are reabsorbed easily through passive diffusion.

Drug Elimination Factors

Drug characteristics (polarity, size, pKa) influence clearance rates.
Genetic variations and diseases affect metabolism and elimination, particularly first-pass metabolism.
Hepatic clearance relates to blood flow to the liver, intrinsic clearance, and drug-protein binding fractions.
Renal clearance is determined by GFR, tubular secretion, and reabsorption processes.

Description

Test your knowledge on drug metabolism and excretion processes. This quiz covers key concepts such as administration routes, absorption, distribution, and the roles of the liver and kidneys in drug metabolism. Understand how active drugs are converted to inactive forms and how their excretion is facilitated.