Introduction to Pharmacology Quiz

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Questions and Answers

Which factor primarily affects the absorption rate of a drug based on its molecular weight?

Lower molecular weight leads to decreased absorption.

Higher molecular weight leads to increased absorption.

Molecular weight does not affect absorption.

Higher molecular weight leads to decreased absorption. (correct)

Why is a non-ionized drug more likely to be absorbed in the gastrointestinal tract?

It is lipid-soluble and diffusible. (correct)

It has a lower pKa value.

It is water-soluble and easily diffuses.

It is better formulated for absorption.

How does pH influence drug ionization?

Basic drugs become less ionized in acidic solutions.

Ionization of drugs is independent of pH.

Acidic drugs are more ionized in alkaline solutions. (correct)

All drugs are ionized at neutral pH.

What happens to aspirin in the stomach due to its pKa?

It becomes non-ionized and enters gastric mucosal cells. Signup and view all the answers

What is the role of pKa in drug absorption?

It indicates the solubility of the drug at a specific pH. Signup and view all the answers

How can urine pH be manipulated for drug excretion in cases of toxicity?

Acidify urine for acidic drug toxicity. Signup and view all the answers

Which of the following factors can affect drug absorption?

Both drug properties and patient factors. Signup and view all the answers

Which scenario correctly reflects the influence of ionization on drug pharmacokinetics?

Ionized drugs are more likely to be excreted by the kidneys. Signup and view all the answers

What is the primary effect of drug molecular weight on absorption?

Higher molecular weight decreases absorption. Signup and view all the answers

How does the ionization of a drug influence its ability to diffuse across cell membranes?

Ionized drugs cannot cross cell membranes effectively. Signup and view all the answers

Which statement about the pKa of a drug is correct?

pKa is the pH where 50% of the drug is ionized and 50% is non-ionized. Signup and view all the answers

What happens to aspirin when it is ionized in the alkaline environment of the kidney?

It gets excreted more efficiently. Signup and view all the answers

Which factor would likely decrease the absorption of a drug in the gastrointestinal tract?

Increasing the patient's gastric pH. Signup and view all the answers

In which condition would urine alkalinization be particularly beneficial?

Acidic drug toxicity, such as that from aspirin. Signup and view all the answers

What impact does drug formulation have on absorption?

Formulation can directly influence the drug's ionization. Signup and view all the answers

Which attribute of a drug promotes its absorption in the body?

Being non-ionized. Signup and view all the answers

Study Notes

Introduction to Pharmacology

Pharmacology is the study of drugs and their effects on living organisms.
Pharmacokinetics is the study of what the body does to a drug.
Pharmacodynamics is the study of what a drug does to the body.

Pharmacokinetics - ADME

Absorption: the passage of a drug from the site of administration into the bloodstream.
Distribution: the process of a drug moving from the bloodstream to the tissues and organs
Metabolism: the process of breaking down drugs in the body, primarily in the liver
Excretion: the process of removing drugs from the body, mainly via the kidneys

Factors Affecting Drug Absorption

Drug Factors:
- Molecular Weight: Lower molecular weight drugs absorb more easily.
- Lipophilicity: Lipid-soluble drugs absorb more readily than water-soluble drugs.
- Solubility: Non-ionized drugs are lipid-soluble and can pass through cell membranes easily. Ionized drugs are water-soluble and have difficulty crossing cell membranes.
- pKa:
  - The pH of the medium (e.g., body fluid) and the pKa of the drug determine the degree of ionization.
  - pKa represents the pH at which 50% of the drug is ionized and 50% is non-ionized.

Clinical Significance of pKa

In the Gastrointestinal Tract (GIT):
- Aspirin, a weak acid with a pKa of 3.5, is non-ionized in the stomach. This allows it to easily cross the cell membrane and enter gastric mucosal cells where it becomes trapped. This can lead to cell death and peptic ulceration.
In the Kidneys:
- Drug ionization increases renal excretion.
- To increase excretion of acidic drugs like aspirin, urine can be alkalinized.
- To increase excretion of basic drugs like amphetamine, urine can be acidified.

Introduction to Pharmacology

Pharmacology is a quantitative study of drugs, specifically how the body processes and responds to them.
Pharmacokinetic refers to the movement of drugs through the body, encompassing four key processes:
- Absorption
- Distribution
- Metabolism
- Excretion
Absorption is the initial process where a drug enters the bloodstream from its administration site.

Factors Affecting Drug Absorption

Factors affecting drug absorption can be categorized into two groups:
- Drug properties
- Patient Factors

Drug Properties

Molecular weight (MW) plays a crucial role in absorption:
- Lower MW drugs generally exhibit higher absorption rates.
- Higher MW drugs typically show slower absorption.
- Example: Procaine penicillin (PP) is a large molecule and therefore has limited absorption.
Lipophilicity (lipid solubility): Highly lipid-soluble drugs readily pass through cell membranes and are absorbed more efficiently.
Solubility: Whether a drug is soluble in water or lipids influences its ability to cross cell membranes:
- Non-ionized drugs are typically lipid-soluble and can easily diffuse across cell membranes.
- Ionized drugs are water-soluble and have difficulty passing through cell membranes.

Ionization and pKa

Drugs can exist in ionized and non-ionized forms within solutions.
The degree of ionization depends on:
- pH of the solution
- pKa of the drug (dissociation constant)
pKa represents the pH at which a drug is 50% ionized and 50% non-ionized.

Acidic vs Basic Drugs

Acidic drugs:
- Tend to be ionized in basic environments
- Remain non-ionized in acidic environments, leading to higher absorption.
Basic drugs:
- Tend to be ionized in acidic environments
- Remain non-ionized in basic environments, leading to higher absorption.

Clinical Significance of pKa

Gastrointestinal Tract (GIT):
- Aspirin (weak acid, pKa 3.5) remains non-ionized in the acidic stomach, readily crossing cell membranes and entering gastric mucosal cells.
- Aspirin can become trapped within these cells, causing damage and potentially leading to peptic ulceration.
Kidney:
- Ionized drugs are more easily excreted by the kidneys. Therefore:
  - Alkalinization of urine can enhance the excretion of acidic drugs (e.g., Aspirin overdose).
  - Acidification of urine can promote the excretion of basic drugs (e.g., Amphetamine toxicity).

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Description

Test your knowledge on the basics of pharmacology, including pharmacokinetics and pharmacodynamics. This quiz covers the key concepts of drug absorption, distribution, metabolism, and excretion. Dive into factors affecting drug absorption and see how well you understand the subject.