Podcast
Questions and Answers
What is indicated by the ratio F in pharmacokinetics?
What is indicated by the ratio F in pharmacokinetics?
- The rate of drug absorption
- The bioavailability of a drug (correct)
- The extent of drug metabolism
- The dosage form of a medication
Which factor would enhance the bioavailability of a drug administered orally?
Which factor would enhance the bioavailability of a drug administered orally?
- Higher dosage form particle size
- Increased lipid solubility of the drug (correct)
- Lower local blood flow at the site of administration
- Higher molecular weight of the drug
Which drug characteristic would most likely result in slower absorption when administered orally?
Which drug characteristic would most likely result in slower absorption when administered orally?
- Liquid dosage form
- High local blood flow
- Large molecular size (correct)
- High lipid solubility
What is commonly true about the absorption of weak acids in comparison to weak bases?
What is commonly true about the absorption of weak acids in comparison to weak bases?
When comparing intravenous (IV) administration of a drug to oral (p.o.) administration, what is a major consideration?
When comparing intravenous (IV) administration of a drug to oral (p.o.) administration, what is a major consideration?
What is the primary effect of macrolide antibiotics on Pgp substrates?
What is the primary effect of macrolide antibiotics on Pgp substrates?
Which route of administration avoids the absorption process entirely?
Which route of administration avoids the absorption process entirely?
Which factor does NOT improve absorption via the oral route?
Which factor does NOT improve absorption via the oral route?
What type of administration makes systemic absorption less effective when topical effects are required?
What type of administration makes systemic absorption less effective when topical effects are required?
What characteristic of drugs enhances absorption through the topical route?
What characteristic of drugs enhances absorption through the topical route?
What does a Volume of Distribution (Vd) value greater than total body fluids indicate?
What does a Volume of Distribution (Vd) value greater than total body fluids indicate?
In a 70 kg adult, what is the approximate plasma volume?
In a 70 kg adult, what is the approximate plasma volume?
Which situation is likely to cause a decrease in Volume of Distribution?
Which situation is likely to cause a decrease in Volume of Distribution?
What is the typical Volume of Distribution for total body fluids in a 70 kg adult?
What is the typical Volume of Distribution for total body fluids in a 70 kg adult?
What does a Vd equal to plasma volume suggest about a drug's distribution?
What does a Vd equal to plasma volume suggest about a drug's distribution?
Which factor does NOT typically influence the Volume of Distribution?
Which factor does NOT typically influence the Volume of Distribution?
How is Volume of Distribution expressed per kg in a 70 kg adult?
How is Volume of Distribution expressed per kg in a 70 kg adult?
A condition that leads to selective distribution of a drug would most likely occur under which circumstance?
A condition that leads to selective distribution of a drug would most likely occur under which circumstance?
What is a primary characteristic of body depots for drug storage?
What is a primary characteristic of body depots for drug storage?
Which type of drugs can easily cross the Blood-Brain Barrier?
Which type of drugs can easily cross the Blood-Brain Barrier?
How does the Blood-CSF Barrier impact drug permeability?
How does the Blood-CSF Barrier impact drug permeability?
What is a possible outcome of diuretic therapy regarding plasma levels?
What is a possible outcome of diuretic therapy regarding plasma levels?
Depot injections are typically used for which purpose?
Depot injections are typically used for which purpose?
Which factor is NOT typically a barrier to drug diffusion?
Which factor is NOT typically a barrier to drug diffusion?
What role do depot tissues play in pharmacokinetics?
What role do depot tissues play in pharmacokinetics?
When considering drug administration, which barrier is crucial for CNS-targeting drugs?
When considering drug administration, which barrier is crucial for CNS-targeting drugs?
What is pharmacokinetics concerned with?
What is pharmacokinetics concerned with?
Absorption of drugs primarily occurs through which mechanism?
Absorption of drugs primarily occurs through which mechanism?
What does bioavailability measure?
What does bioavailability measure?
Which route of administration generally does NOT rely on absorption?
Which route of administration generally does NOT rely on absorption?
What aspect is NOT a part of the absorption process?
What aspect is NOT a part of the absorption process?
In drug absorption, pinocytosis and phagocytosis are examples of what type of mechanisms?
In drug absorption, pinocytosis and phagocytosis are examples of what type of mechanisms?
Which of the following involves filtration in the drug absorption process?
Which of the following involves filtration in the drug absorption process?
Which statement about the permeation of drugs across membranes is incorrect?
Which statement about the permeation of drugs across membranes is incorrect?
Study Notes
General Pharmacology Overview
- Pharmacology involves the study of drugs and their effects on biological systems.
- Key branches include pharmacokinetics (drug absorption, distribution, metabolism, excretion) and pharmacodynamics (drug action).
Pharmacokinetics
- Defined as "What a Body Does to the Drug."
- Focuses on absorption, distribution, metabolism, and elimination.
Absorption of Drugs
- Movement of drugs from the site of administration to systemic circulation.
- Main routes: oral, intravenous (IV), subcutaneous (SC), and intramuscular (IM).
- Mechanisms of absorption involve passive diffusion, active transport, facilitated diffusion, and endocytosis.
Bioavailability
- Bioavailability (F) indicates the rate and extent a drug is absorbed into circulation.
- IV medications have 100% bioavailability (F = 1); oral medications may require larger doses due to lower F.
Factors Affecting Bioavailability
- Drug absorption, gut wall metabolism, and hepatic first-pass effect can lower effective drug concentration.
- Drugs with high lipid solubility (e.g., anesthetics) diffuse rapidly across cell membranes.
- Local blood flow enhances absorption; e.g., intestines have greater blood flow than the stomach.
- Molecular size and drug formulation impact absorption rate (solutions > suspensions > tablets).
Drug Ionization and pH
- Drug ionization affects absorption; weak acids and bases demonstrate variable absorption based on pH.
- Overexpression of P-glycoprotein (Pgp) in certain tumors can lead to multi-drug resistance.
Administration Routes
- Systemic Routes: Enteral (oral, rectal), parenteral (IV, SC, IM).
- Oral absorption is favored when drugs are lipid-soluble and the stomach is empty.
- Parenteral routes (IV, SC, IM) avoid absorption issues and enable faster action.
- Local Routes: Topical, inhalational, intranasal, conjunctival.
- Systemic absorption from topical applications is influenced by drug lipophilicity and skin condition.
Volume of Distribution (Vd)
- Vd indicates how extensively a drug disperses in body fluids.
- Plasma volume is approximately 3.5-4.5 L; total body water is around 40 L.
- Conditions like congestive heart failure may alter drug distribution and concentrations.
Drug Depots and Barriers
- Depots are body compartments for slow drug release (e.g., fat stores lipophilic drugs).
- Barriers limit drug diffusion, including:
- Blood-Brain Barrier: Lipid-soluble drugs cross easily.
- Blood-CSF Barrier: Water-soluble and larger drugs cross with difficulty.
- Placental Barrier: Influences drug transfer during pregnancy.
Considerations for Drug Administration
- Route of administration is critical for drugs intended to target specific sites, especially when crossing biological barriers.
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Description
Test your knowledge on drug bioavailability, its definition, and the factors affecting it. This quiz explores the concepts of rate and extent of absorption, and how they impact drug administration methods. Gain insights into why certain drugs may need higher oral doses due to low bioavailability.
