Absorption Kinetics
Absorption Kinetics - Related Videos
00:23
Kinetic Energy
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2019
Kinetic energy is the ability of an object in motion to do work or enact change. It can take on many forms. For instance, water flowing down a waterfall has kinetic energy. In biological systems, particles of light travel and are absorbed by plants to create chemical energy. Animals consume the chemical energy and give off molecules that carry their scent through the air. They also generate kinetic energy when they run away from predators. Entire systems also possess kinetic energy, like the...
01:19
Enzyme Kinetics
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2019
Enzymes speed up reactions by lowering the activation energy of the reactants. The speed at which the enzyme turns reactants into products is called the rate of reaction. Several factors impact the rate of reaction, including the number of available reactants. Enzyme kinetics is the study of how an enzyme changes the rate of a reaction. Scientists typically study enzyme kinetics with a fixed amount of enzyme in the controlled environment of a test tube. When more reactant, or substrate, is...
03:07
Kinetic Molecular Theory: Molecular Velocities, Temperature, and Kinetic Energy
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2020
The kinetic molecular theory qualitatively explains the behaviors described by the various gas laws. The postulates of this theory may be applied in a more quantitative fashion to derive these individual laws. Collectively, the molecules in a sample of gas have average kinetic energy and average speed; but individually, they move at different speeds. Molecules frequently undergo elastic collisions in which the momentum is conserved. Since the colliding molecules are deflected off at different...
08:07
Enzyme Assays and Kinetics
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2023
Enzyme kinetics describes the catalytic effects of enzymes, which are biomolecules that facilitate chemical reactions necessary for living organisms. Enzymes act on molecules, referred to as substrates, to form products. Enzyme kinetic parameters are determined via assays that directly or indirectly measure changes in substrate or product concentration over time. This video will cover the basic principles of enzyme kinetics (including rate equations) and kinetic models. The concepts governing...
01:19
Drug Absorption: Factors Affecting GI Absorption
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2023
The process of oral drug absorption can be influenced by several factors. Weakly acidic drugs tend to be absorbed more readily from the stomach due to their nonionized state. However, absorption may be less efficient in the upper intestine, where drugs are often ionized. Interestingly, despite the stomach's apparent advantage for drug absorption, its mucous layer can hinder diffusion. Its surface area is also smaller than the intestine's, which can further slow down the absorption rate. In...
FAQs
Dissolution, membrane permeability, gastrointestinal conditions, formulation, and local blood flow jointly influence the speed of uptake. A drug must first become available from its dosage form, cross biological membranes, and encounter sufficient perfusion for entry into circulation. Changes in any of these steps can alter the concentration-time profile, shifting the timing and magnitude of clinical effects.
First-order input changes according to the amount of drug remaining at the absorption site, whereas zero-order input supplies drug at a relatively constant rate. These different input patterns produce distinct concentration-time profiles and can influence onset, peak behavior, and duration. Recognizing the pattern helps pharmacologists interpret how a formulation or administration process shapes exposure.
The absorption rate constant characterizes the rate of drug input, while bioavailability describes the fraction reaching systemic circulation. A drug may enter circulation rapidly but incompletely, or slowly with a greater overall fraction absorbed. Considering both measures prevents rate and extent from being treated as interchangeable and supports more meaningful comparisons among dosing conditions or formulations.
Researchers use concentration-time data and pharmacokinetic models to evaluate how formulations alter absorption rate, extent, and profile. Model-based comparisons can identify delayed or incomplete uptake and estimate parameters such as the absorption rate constant and bioavailability. These results help determine whether observed differences reflect the formulation, gastrointestinal conditions, or another factor affecting drug entry.
Altered gastrointestinal conditions, differences in formulation, limited dissolution, reduced membrane permeability, or changes in blood flow can delay or reduce uptake. The resulting exposure may show a later effect, lower systemic availability, or a changed concentration-time pattern. Identifying these possibilities helps clinicians interpret unexpected responses and consider whether altered absorption contributes to variable drug effects.
Absorption information helps connect a dosing regimen with the timing and magnitude of systemic exposure. Clinicians and pharmacologists can use absorption parameters and concentration-time profiles to compare regimens, anticipate altered exposure, and interpret therapeutic monitoring results. This is particularly relevant when delayed or incomplete uptake, formulation differences, or interactions may change the expected clinical response.