Pharmacology: Drug Absorption and Distribution

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Questions and Answers

Which factor does NOT affect drug absorption?

Drug dose

Molecular weight

Color of the tablet (correct)

Local effect of drug

What route of administration is mentioned for drug absorption?

Intramuscular

Sublingual (correct)

Inhalation

Topical

How does blood flow affect absorption?

Enhances absorption at the site (correct)

Decreases surface area

Reduces drug dose

Increases contact time

Which dosage form is identified as having an effect on absorption?

Sustained-release tablets Signup and view all the answers

What does a greater surface area generally do to drug absorption?

Enhances rate of absorption Signup and view all the answers

Which of the following factors is NOT drug-related?

Age of the patient Signup and view all the answers

What is a characteristic of sustained-release tablets?

Prolonged effect Signup and view all the answers

Which aspect is important for ensuring absorption occurs effectively?

Contact time at the absorption site Signup and view all the answers

What is the major site of drug metabolism in the body?

Liver Signup and view all the answers

Which of the following phases of metabolism involves the conversion of lipophilic molecules into more polar molecules?

Phase I Signup and view all the answers

What type of drug is a prodrug?

An inactive form that converts to active after metabolism Signup and view all the answers

What is the effect of lipophilic drugs in terms of solubility and accumulation?

They may accumulate in body tissues and organs Signup and view all the answers

What type of reactions are involved in Phase I metabolism?

Hydrolysis, oxidation, and reduction Signup and view all the answers

Which of the following is not a characteristic of the Blood Brain Barrier?

It is permeable to all drugs Signup and view all the answers

What is a common drawback of chronic use of drugs that accumulate in body tissues?

Potential for toxicity Signup and view all the answers

Which of the following is not a typical metabolite from Phase I reactions?

Unmodified drugs Signup and view all the answers

What is the outcome of Phase II metabolism?

Conjugation with endogenous substances Signup and view all the answers

Which of the following terms describes the biotransformation of a drug for easier elimination?

Metabolism Signup and view all the answers

What is the primary function of microsomal enzymes in drug metabolism?

They catalyze most phase I reactions. Signup and view all the answers

Which phase of drug metabolism involves glucuronide conjugation?

Phase II Signup and view all the answers

Where are non-microsomal enzymes primarily found?

Cytoplasm and mitochondria Signup and view all the answers

What is the primary aim of drug metabolism?

To produce more water soluble compounds Signup and view all the answers

What type of reaction is primarily associated with phase I drug metabolism?

Oxidation and reduction Signup and view all the answers

What is the primary role of drug-metabolizing enzymes?

To convert lipophilic drugs into water-soluble forms Signup and view all the answers

What type of metabolism involves metabolizing a constant ratio of the drug over time?

First order metabolism Signup and view all the answers

What is a characteristic of phase I metabolic reactions?

They often introduce polar functional groups. Signup and view all the answers

Which statement correctly describes zero order metabolism?

A constant amount of drug is metabolized per unit of time Signup and view all the answers

Which type of enzymes are responsible for most phase II reactions except glucuronide acid conjugation?

Cytoplasmic enzymes Signup and view all the answers

What is meant by 'first pass metabolism'?

The initial metabolism of a drug before it reaches systemic circulation Signup and view all the answers

What classification do enzymes like CYP450 belong to?

Microsomal enzymes Signup and view all the answers

What does half-life refer to in drug metabolism?

The time it takes for half of the drug to be eliminated Signup and view all the answers

What is the overall significance of increasing the water solubility of drugs during metabolism?

It facilitates easier excretion from the body Signup and view all the answers

What factor increases the absorption of a drug at the absorption site?

Increased contact time at the absorption site Signup and view all the answers

How does lipid solubility affect drug absorption?

Drugs that dissolve in lipids are absorbed more efficiently Signup and view all the answers

What happens to acidic drugs in a basic environment?

They become charged and are less likely to be absorbed Signup and view all the answers

What role does available surface area play in drug absorption?

Larger surface area enhances absorption efficiency Signup and view all the answers

Which of the following statements about drug ionization is correct?

The pH of the environment affects the ionization of drugs Signup and view all the answers

What effect does diarrhea have on absorption?

It decreases the available surface area for absorption Signup and view all the answers

Study Notes

Absorption

Key factors in drug absorption include blood flow to sites, contact time, and molecular weight.
Lipid solubility is crucial, as it combines drug lipophilicity and ionization, influenced by pH.
Acidic drugs become charged in basic environments, while basic drugs become charged in acidic settings.
Sustained-release formulations, dosage forms, and route of administration affect absorption efficiency.
Increased available surface area (e.g., intestines) enhances absorption, particularly with altered conditions like diarrhea.

Distribution

Drugs can redistribute to adipose tissue, potentially leading to prolonged effects and toxicity.
The Blood-Brain Barrier restricts access to the brain, allowing only uncharged, lipid-soluble drugs to penetrate.

Metabolism

Metabolism refers to the transformation of drugs for easier elimination, primarily occurring in the liver.
Biotransformation can convert drugs from active to inactive forms or vice versa (prodrugs).
Phase I reactions modify lipophilic molecules to form more polar molecules through oxidation, reduction, or hydrolysis.
Phase II reactions involve conjugation where endogenous groups are added to functional groups, enhancing water solubility.

Drug-Metabolizing Enzymes

Microsomal enzymes (e.g., CYP450) are critical for Phase I reactions and some Phase II reactions, located in the endoplasmic reticulum of hepatocytes.
Non-microsomal enzymes cater to Phase II reactions other than glucuronidation and are located in various cellular compartments.

Kinetics of Metabolism

First-order metabolism indicates a constant ratio of drug elimination per time, characterized by a half-life.
Zero-order metabolism signifies a constant amount of drug eliminated per time, which may occur at high drug concentrations.

First Pass Metabolism

First-pass metabolism occurs when drugs metabolized in the liver reduce bioavailability prior to systemic circulation.
The extent of first-pass metabolism affects the efficacy and dosing of orally administered drugs.

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Description

Explore the key factors influencing drug absorption, distribution, and metabolism in the human body. This quiz covers essential concepts such as lipid solubility, the Blood-Brain Barrier, and drug biotransformation. Test your knowledge of how various factors affect drug efficacy and safety.