Podcast
Questions and Answers
Which factor does NOT significantly influence the rate and extent of drug absorption?
Which factor does NOT significantly influence the rate and extent of drug absorption?
What mechanism primarily allows small hydrophilic molecules to be absorbed across the cell membrane?
What mechanism primarily allows small hydrophilic molecules to be absorbed across the cell membrane?
In the context of drug absorption, the double peak phenomenon is most commonly associated with which aspect?
In the context of drug absorption, the double peak phenomenon is most commonly associated with which aspect?
How does gastric emptying influence drug absorption?
How does gastric emptying influence drug absorption?
Signup and view all the answers
What physiological factor can lead to changes in drug bioavailability?
What physiological factor can lead to changes in drug bioavailability?
Signup and view all the answers
What best describes the enterohepatic circulation in relation to drug absorption?
What best describes the enterohepatic circulation in relation to drug absorption?
Signup and view all the answers
Which factor can significantly influence the occurrence of the double peak phenomenon in drug absorption?
Which factor can significantly influence the occurrence of the double peak phenomenon in drug absorption?
Signup and view all the answers
Which of the following best describes the relationship between gastric emptying and drug absorption?
Which of the following best describes the relationship between gastric emptying and drug absorption?
Signup and view all the answers
What impact does pH have on drug movement through biological membranes?
What impact does pH have on drug movement through biological membranes?
Signup and view all the answers
Which statement about the role of the gastrointestinal tract in drug absorption is accurate?
Which statement about the role of the gastrointestinal tract in drug absorption is accurate?
Signup and view all the answers
What is the primary reason for recommending strategies to improve oral drug absorption?
What is the primary reason for recommending strategies to improve oral drug absorption?
Signup and view all the answers
Which mechanism is crucial for the active transport of drugs across cellular membranes?
Which mechanism is crucial for the active transport of drugs across cellular membranes?
Signup and view all the answers
What factors can affect the systemic absorption of an oral drug?
What factors can affect the systemic absorption of an oral drug?
Signup and view all the answers
What is the primary factor driving the passive diffusion of drugs in oral absorption?
What is the primary factor driving the passive diffusion of drugs in oral absorption?
Signup and view all the answers
Which of the following factors increases the rate of passive diffusion for drugs?
Which of the following factors increases the rate of passive diffusion for drugs?
Signup and view all the answers
How does the thickness of the membrane affect drug diffusion?
How does the thickness of the membrane affect drug diffusion?
Signup and view all the answers
Which area of the gastrointestinal tract is associated with the highest rate of drug absorption due to increased surface area?
Which area of the gastrointestinal tract is associated with the highest rate of drug absorption due to increased surface area?
Signup and view all the answers
Which phenomenon describes a situation where there are two peaks in drug concentration observed in the plasma after administration?
Which phenomenon describes a situation where there are two peaks in drug concentration observed in the plasma after administration?
Signup and view all the answers
What effect does increased temperature generally have on drug absorption?
What effect does increased temperature generally have on drug absorption?
Signup and view all the answers
What role does the partition coefficient play in drug absorption?
What role does the partition coefficient play in drug absorption?
Signup and view all the answers
How does enterohepatic circulation affect drug concentrations in the body?
How does enterohepatic circulation affect drug concentrations in the body?
Signup and view all the answers
Which statement accurately describes gastric emptying in relation to drug absorption?
Which statement accurately describes gastric emptying in relation to drug absorption?
Signup and view all the answers
Which type of barrier is more challenging for drug molecules to cross due to its structure?
Which type of barrier is more challenging for drug molecules to cross due to its structure?
Signup and view all the answers
What happens to weak acids in an alkaline environment regarding absorption?
What happens to weak acids in an alkaline environment regarding absorption?
Signup and view all the answers
What is the impact of an acidic environment on the absorption of basic drugs?
What is the impact of an acidic environment on the absorption of basic drugs?
Signup and view all the answers
In the context of drug absorption, what does the pH-partition hypothesis propose?
In the context of drug absorption, what does the pH-partition hypothesis propose?
Signup and view all the answers
Which of the following best describes the absorption of drugs in the stomach compared to the small intestine?
Which of the following best describes the absorption of drugs in the stomach compared to the small intestine?
Signup and view all the answers
What happens to the total drug concentration on either side of a membrane with differing pH levels?
What happens to the total drug concentration on either side of a membrane with differing pH levels?
Signup and view all the answers
What is likely to happen to weak acids if they encounter a highly basic environment?
What is likely to happen to weak acids if they encounter a highly basic environment?
Signup and view all the answers
What phenomenon describes the occurrence of two distinct peaks in drug concentration over time after administration?
What phenomenon describes the occurrence of two distinct peaks in drug concentration over time after administration?
Signup and view all the answers
How does gastric emptying affect drug absorption?
How does gastric emptying affect drug absorption?
Signup and view all the answers
What role does enterohepatic circulation play in drug absorption?
What role does enterohepatic circulation play in drug absorption?
Signup and view all the answers
Study Notes
Biopharmaceutics and Drug Absorption
- Biopharmaceutics examines the interplay of drug properties, dosage forms, and routes of administration on systemic drug absorption.
- Learning objectives include describing cell membrane characteristics, mechanisms for absorption, transporters involved, pH influence, physiological factors, first-pass effect, enterohepatic cycling, and the impact of food/disease on absorption. Strategies for enhancing oral drug absorption are also considered.
Cell Membrane Structure and Mechanisms
- Biological membranes act as barriers to drug delivery.
- Transcellular absorption involves movement across cells, often through lipophilic molecules.
- Paracellular absorption occurs between cells, generally via small hydrophilic molecules.
- Some drugs use both mechanisms
- The fluid mosaic model describes the cell membrane's structure, with proteins embedded in a lipid bilayer.
Passive Diffusion
- Molecules move from higher to lower concentrations.
- No energy is expended.
- An important mechanism for many drugs.
- Directly related to temperature.
- Inversely related to molecular size.
- Affected by Fick's Law (rate of diffusion): dQ/dt = DAK (CGI - Cp)/h .
- Factors impacting passive diffusion include the concentration gradient (driving force), the partition coefficient (lipid solubility), the surface area of the membrane, and membrane thickness.
Active Transport
- Transport against the concentration gradient
- Energy-consuming.
- Important process for drug absorption and secretion
- Carrier protein are highly selective for the drug (structure-specific)
- Saturable at high concentration of drug(amount of carrier )
- Affected by competitive inhibition from similar substances
Membrane Transport Proteins
- Carrier and channel proteins are important for drug absorption in the intestines, liver, kidneys, and brain.
- Influx transporters increase drug absorption, while efflux transporters decrease it.
- Specific examples of carriers like OATP2, OATP6, OCT1 (and substrates) are crucial.
- ATP-binding cassette (ABC) transporters (eg., P-glycoprotein) play critical roles in drug multidrug resistance.
Weak Electrolytes and pH
- Most drugs are weak acids or bases existing in ionized and non-ionized forms.
- Ionization is affected by pH and pKa.
- Non-ionized forms are lipophilic and more easily absorbed. The ionized forms are more water soluble.
- The Henderson-Hasselbalch equation describes the relationship between pH and pKa.
pH-partition Hypothesis
- Differences in pH across a membrane influence drug ionization and absorption. Ionized forms are generally less absorbed than non-ionized forms. The compartment with higher ionization will contain a higher concentration of the total amount.
Effect of Food on Drug Absorption
- Food can affect drug absorption by altering pH, motility, and the enzyme activity.
- Food reduces certain drug absorption but increase the absorption of some basic drugs.
- Some drugs are best taken with food (e.g., lipophilic substances).
- Other drugs may be harmful taken with food (e.g., antibiotics).
First-pass Effect
- Elimination of drug by the liver or gut during the first pass through the systemic circulation.
- Can significantly decrease the bioavailability of the drug.
- First-pass effect can reduce or eliminate the drug's systemic effectiveness.
Enterohepatic Circulation
- Drug absorption, secretion into bile, storage in gallbladder, re-absorption from intestine and returning to circulation.
- This cycle can prolong drug exposure times and may increase the amount of drug in the body.
Double Peak Phenomenon
- Some drugs exhibit a double-peaked plasma concentration curve after a single dose.
- This is often due to differences in gastric emptying, drug dissolution, and enterohepatic circulation.
Effect of Disease on GI Drug Absorption
- Disease-related conditions such as CHF, Parkinson's, and Celiac disease can affect drug absorption.
- Altered blood flow, GI motility, and permeability or gastric pH can change the amount of drug absorbed.
Effect of Drugs on GI Drug Absorption
- Drugs (e.g., antacids, anticholinergics, antidepressants) affect GI tract functions, which alter drug absorption.
Effect of Nutrients on GI Drug Absorption
- Nutrients can impact drug absorption, specifically relevant to calcium, dietary fiber, grapefruit juice, and others.
General Important Info
- Bioavailability is the fraction of administered drug reaching the systemic circulation, and this is frequently impacted by the properties of the drug and physiological factors.
- This is an overview, and specific situations and drug entities need to be considered for detailed information and specific recommendations.
Colonic Drug Delivery
- Some drugs are optimized for colonic delivery. This is useful if they are broken down in the stomach and small intestine.
- Drugs formulated and optimized for colonic absorption might be effective treating local symptoms in the large intestine area.
Drug Absorption and Transport Mechanisms
- Absorption of a drug can happen by various mechanisms, passive diffusion and/or active transport. Knowing the specific delivery method is helpful in determining when a drug is delivered to the target.
Important Considerations
- Many factors influence drug absorption in the gastrointestinal (GI) tract.
- Appropriate consideration of these factors is essential for optimal therapeutic outcomes and to avoid negative side effects.
Studying That Suits You
Use AI to generate personalized quizzes and flashcards to suit your learning preferences.
Related Documents
Description
Test your knowledge on key concepts related to drug absorption in this pharmacology quiz. Explore factors influencing drug bioavailability, mechanisms of absorption, and the effects of gastric emptying. Understand the significance of the double peak phenomenon in drug kinetics.
