Passive Diffusion: Movement of drug molecules across cell membranes from an area of higher to lower concentration without energy, primarily influenced by lipophilicity and ionization state.
Facilitated Diffusion: Carrier-mediated transport that allows molecules to cross membranes along their concentration gradient without energy expenditure, often specific to certain drugs.
Active Transport: Energy-dependent process where drugs are transported against their concentration gradient via carrier proteins, affecting absorption especially for nutrients and some drugs.
Endocytosis: Cellular process where the cell engulfs external substances into vesicles, allowing for absorption of larger molecules or particles.
Bioavailability (F): The proportion of an administered dose that reaches systemic circulation unchanged, influenced by absorption and first-pass metabolism.
1. Which of the following best defines 'drug absorption mechanisms' in pharmacology?
2. According to the course content on factors affecting absorption, how does pH influence the absorption of weak acids and weak bases?
3. What is the primary role of the volume of distribution (Vd) in pharmacokinetics?
Drug Absorption Mechanisms — primary?
Passive diffusion is the main mechanism.
Factors affecting absorption — key?
pH, surface area, blood flow, formulation.
Volume of Distribution — meaning?
Theoretical volume relating drug amount to plasma concentration.
Passive Diffusion — mechanism?
Drugs cross membranes down concentration gradient, no energy.
Facilitated Diffusion — difference?
Carrier-mediated, no energy, specific to drugs.
Active Transport — process?
Energy-dependent, moves against gradient via carriers.
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