Podcast
Questions and Answers
Which of the following is NOT a factor affecting the rate of drug absorption?
Which of the following is NOT a factor affecting the rate of drug absorption?
- Blood flow at the site of administration
- Molecule size
- Lipophilicity
- Taste of the drug (correct)
Drugs can be absorbed through intravenous administration.
Drugs can be absorbed through intravenous administration.
False (B)
What is the main purpose of drug absorption?
What is the main purpose of drug absorption?
To allow drugs to reach their site of action in the bloodstream.
The passage of a drug into the systemic circulation from the site of administration is called __________.
The passage of a drug into the systemic circulation from the site of administration is called __________.
Match the following absorption factors with their definitions:
Match the following absorption factors with their definitions:
What is a characteristic of large molecule drugs in terms of absorption?
What is a characteristic of large molecule drugs in terms of absorption?
Ionised drugs are typically absorbed more quickly than non-ionised drugs.
Ionised drugs are typically absorbed more quickly than non-ionised drugs.
The __________ coefficient is used to determine the rate at which a drug can pass through cell membranes.
The __________ coefficient is used to determine the rate at which a drug can pass through cell membranes.
What does pKa represent?
What does pKa represent?
Drugs with pKa values close to 14 are considered weak acids.
Drugs with pKa values close to 14 are considered weak acids.
What is the relationship between pH and the absorption of weak acids?
What is the relationship between pH and the absorption of weak acids?
The formula for calculating pKa is pKa = -log ______.
The formula for calculating pKa is pKa = -log ______.
Match the following terms with their definitions:
Match the following terms with their definitions:
What is an example of a drug that may have absorption difficulties due to high pKa?
What is an example of a drug that may have absorption difficulties due to high pKa?
Zero order kinetics occur independently of drug concentration.
Zero order kinetics occur independently of drug concentration.
What two parameters are critical to determine the oral bioavailability of a drug?
What two parameters are critical to determine the oral bioavailability of a drug?
What is the primary site for the absorption of orally administered drugs?
What is the primary site for the absorption of orally administered drugs?
Liquid pharmaceutical forms generally take longer to absorb compared to solid forms.
Liquid pharmaceutical forms generally take longer to absorb compared to solid forms.
Name one physiological factor that affects the absorption of drugs from the gastrointestinal tract.
Name one physiological factor that affects the absorption of drugs from the gastrointestinal tract.
The rate of absorption is generally faster for __________ pharmaceutical forms compared to solid forms.
The rate of absorption is generally faster for __________ pharmaceutical forms compared to solid forms.
Which of the following can delay gastric emptying?
Which of the following can delay gastric emptying?
What impact does taking medication with food have on some drugs?
What impact does taking medication with food have on some drugs?
Metal ions in food can form complexes with drug molecules, potentially reducing absorption.
Metal ions in food can form complexes with drug molecules, potentially reducing absorption.
Match each drug absorption factor with its description:
Match each drug absorption factor with its description:
Which of the following factors can slow down drug absorption when administered intramuscularly?
Which of the following factors can slow down drug absorption when administered intramuscularly?
Drug absorption from solutions is faster than from suspensions or emulsions.
Drug absorption from solutions is faster than from suspensions or emulsions.
What is one reason for converting water-soluble drugs into water-insoluble esters?
What is one reason for converting water-soluble drugs into water-insoluble esters?
The absorption rate is fastest in the mucosa of the __________.
The absorption rate is fastest in the mucosa of the __________.
Match the route of administration with its effect on absorption speed:
Match the route of administration with its effect on absorption speed:
Which physiological conditions can decrease the rate of drug absorption?
Which physiological conditions can decrease the rate of drug absorption?
A high concentration of a drug at the site of administration typically results in slower absorption.
A high concentration of a drug at the site of administration typically results in slower absorption.
Name one example of a drug that can be converted into a water-insoluble form to slow absorption.
Name one example of a drug that can be converted into a water-insoluble form to slow absorption.
What is the primary reason for lipid-soluble drugs accumulating in adipose tissue over time?
What is the primary reason for lipid-soluble drugs accumulating in adipose tissue over time?
Biotransformation can make an inactive drug effective.
Biotransformation can make an inactive drug effective.
Define the virtual volume of distribution (Vd) of a drug.
Define the virtual volume of distribution (Vd) of a drug.
The process where a drug is converted into a more effective or toxic compound is known as __________.
The process where a drug is converted into a more effective or toxic compound is known as __________.
Match the drug-related terms with their definitions:
Match the drug-related terms with their definitions:
Which of the following correctly describes the ion trap phenomenon?
Which of the following correctly describes the ion trap phenomenon?
Give one example of a pro-drug.
Give one example of a pro-drug.
Basic drugs are concentrated on the side with a higher pH.
Basic drugs are concentrated on the side with a higher pH.
Study Notes
ADME
- The acronym ADME refers to the four main processes the body uses to handle drugs: Absorption, Distribution, Metabolism (Biotransformation), and Elimination (Excretion).
Absorption
- Absorption refers to the passage of a drug from its site of administration into the circulatory system.
- The barrier to absorption depends on where the drug is administered:
- Gastrointestinal Tract: First the epithelial layer, then the endothelium of blood vessels
- Intra-tissue Administration (Injection): Endothelium of capillaries in the tissue
- Intravenous Administration: No absorption occurs.
- The rate of absorption is the amount of drug absorbed per unit of time.
- Factors affecting the rate of absorption:
- Drug-Related Factors:
- Physicochemical Properties:
- Molecule Size: Smaller molecules absorb faster than larger ones.
- Lipophilicity: How well a drug dissolves in fat (lipid-soluble).
- Lipid/Water Partition Coefficient: Higher ratio indicates faster diffusion through cell membranes.
- Ionization: Drugs exist in both ionized and non-ionized forms. The non-ionized form is more lipophilic and easily absorbed.
- Pharmaceutical Form and Solvent:
- Solid Pharmaceutical Form: Requires disintegration and dissolution before absorption.
- Liquid Pharmaceutical Forms: Absorption is faster from solutions than suspensions or emulsions.
- Ester Conversion: To slow down absorption, water-soluble drugs are converted into water-insoluble esters.
- Drug Concentration: Higher concentration leads to faster absorption.
- Pharmacological Property:
- Vasoconstrictors: Narrow blood vessels, slowing absorption.
- Vasodilators: Widen blood vessels, accelerating absorption.
- Physicochemical Properties:
- Biological Factors:
- Blood Flow: Lower blood flow at the site of administration reduces absorption rate.
- Surface Area and Permeability: Larger and more permeable surface areas allow for faster absorption.
- Drug-Related Factors:
Passage Through Membranes
- Drug molecules must pass through cell layers to undergo various pharmacokinetic processes.
- pKa: A constant value for a given drug, indicating its acidic or basic character. It determines the drug's ionization state.
- Strong Acids: pKa close to 0
- Strong Bases: pKa close to 14
- Ionization: Drugs can exist in ionized or non-ionized forms. The non-ionized form is more lipophilic and easily passes through membranes.
- pH: A drug's ionization state is influenced by the pH of the surrounding environment.
- This is important for understanding absorption processes.
- Weak Acids: Exist in a higher proportion of non-ionized form at lower pH.
- Weak Bases: Exist in a higher proportion of non-ionized form at higher pH.
- Kinetics of Absorption:
- First Order Kinetics: Absorption rate depends on the drug concentration gradient.
- Zero Order Kinetics: Absorption occurs at a constant rate, independent of the drug concentration.
Absorption of Drugs from the Gastrointestinal Tract and Oral Bioavailability
- Oral Bioavailability: The rate and extent to which an orally administered drug reaches its site of action in the body.
- Depends on the drug's absorption rate and the degree of absorption (percentage of the dose reaching systemic circulation).
- Small Intestine: The primary site of absorption for oral drugs.
- Large surface area and long residence time contribute to its role in absorption.
- Factors Affecting Absorption:
- Pharmaceutical Form:
- Solid: Requires disintegration and dissolution.
- Liquid: Faster absorption than solids.
- Solubility: Oil and water solubility can affect absorption.
- Particle Size: Smaller particles absorb faster.
- Pharmaceutical Form:
- Physiological Factors:
- Gastric Emptying Time: The time it takes for the stomach to empty its contents.
- Intestinal Transit Time: The time it takes for food to travel through the intestines.
- Blood Flow: Lower blood flow to the gastrointestinal tract reduces absorption.
- Effect of Nutrients:
- Food can influence the rate of absorption by delaying gastric emptying and altering gastric acid secretion.
- It's important to take medications on an empty stomach or with food as advised.
- Fluid: Taking drugs with water accelerates and increases absorption.
Redistribution
- Highly Lipid-Soluble Drugs: Initial accumulation in tissues with high blood supply (e.g., brain).
- Over time, these drugs redistribute to tissues with lower blood flow and higher lipid content (e.g., adipose tissue), leading to lower concentrations at the site of action.
Ion Trap
- pH Differences: Drugs can concentrate in body compartments where they are more ionized, due to pH differences.
- This leads to unequal distribution of the drug.
- Acidic Drugs: Concentrate in compartments with higher pH.
- Basic Drugs: Concentrate in compartments with lower pH.
Virtual Distribution Volume (Vd)
- The volume of fluid in which a drug would need to be distributed to achieve the same concentration in plasma as the actual concentration in the body.
Biotransformation (Metabolism) of Drugs
- Biotransformation: Chemical changes that drugs undergo in the body, primarily catalyzed by enzymes.
- Drugs can be transformed into less effective, more effective, or more toxic compounds.
- Bioactivation: Drugs converted into more effective forms through metabolism.
- Pro-Drug: An inactive compound that is metabolized into an active form in the body.
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Description
Evaluate your understanding of the ADME processes in pharmacology, focusing on drug absorption mechanisms. This quiz covers key factors affecting absorption and specific routes of administration. Challenge yourself to deepen your knowledge of drug handling in the body.
