Drug transporters can be saturated if the substrate (drug) levels are sufficiently high. Once the transporter is saturated, no additional drug can be absorbed from the GI tract, even if it is available for transport. Similar to the example of dissolution, increases in the dose will not increase the exposure.
What does saturable mean in pharmacokinetics?
Saturable binding or reabsorption: above a certain drug concentration, drug protein binding or drug reabsorption in kidney tubules tends to reach maximal capacity. This leads to a disproportionate increase in the rate of elimination with increasing drug concentrations (e.g. with high doses of vitamin).
What is a saturable process?
Saturable absorption is a property of materials where the absorption of light decreases with increasing light intensity. Most materials show some saturable absorption, but often only at very high optical intensities (close to the optical damage).
What is drug bioavailability?
Bioavailability refers to the extent a substance or drug becomes completely available to its intended biological destination(s).
What happens in drug absorption?
Before drugs can be clinically effective, they must be absorbed. Absorption is the process of a drug moving from its site of delivery into the bloodstream. The chemical composition of a drug, as well as the environment into which a drug is placed, work together to determine the rate and extent of drug absorption.
What does not saturable mean?
: capable of being saturated.
What is saturable hepatic metabolism?
These metabolic and carrier-mediated excretory clearance pathways are capacity-limited, becoming saturated at sufficiently high substrate concentrations. Saturable metabolic clearance processes lead to dose-dependent pharmacokinetics for many chemicals.
How does a saturable reactor work?
Saturable reactors have a non-linear voltage-current characteristic so that when the voltage across the reactor rises above a certain threshold, the reactor current increases disproportionately due to core saturation. As a result, its effective impedance reduces below that without saturation.
How does a saturable absorber work?
A saturable absorber is an optical component with a certain absorption loss for light, which is reduced at high optical intensities. Such nonlinear absorption can occur, e.g., in a medium with absorbing dopant ions, when a strong optical intensity leads to depletion of the ground state of these ions.
What is reverse saturable absorption?
Reverse saturable absorption. A class of nonlinear absorbers in which the excited state absorption is large compared to the ground state absorption can undergo a process called reverse saturable absorption (RSA), also known as reversible saturable absorption.
What are the 2 types of bioavailability?
One way to resolve this problem is to define “reliable bioavailability” as positive bioavailability results (an absorption meeting a predefined criterion) that include 84% of the trial subjects and “universal bioavailability” as those that include 98% of the trial subjects.
Why is bioavailability important in drugs?
Bioavailability is a key indicator of drug absorption. It represents the administered dose fraction which achieves success in reaching the systemic circulation when administered orally or through any other extravascular dosing route.
What is absolute bioavailability?
“Absolute” bioavailability is the amount of drug from a formulation that reaches the systemic circulation relative to an intravenous (IV) dose. The IV dose is assumed to be 100% bioavailable … since you are injecting the drug directly into the systemic circulation.
What are 4 factors that affect absorption of a drug?
These include:
- physicochemical properties (e.g. solubility)
- drug formulation (e.g. tablets, capsules, solutions)
- the route of administration (e.g. oral, buccal, sublingual, rectal, parenteral, topical, or inhaled)
- the rate of gastric emptying.
How long does it take medication to dissolve in your stomach?
approximately 30 minutes
In general, it typically takes approximately 30 minutes for most medications to dissolve. When a medication is coated in a special coating – which may help protect the drug from stomach acids – often times it may take longer for the therapeutic to reach the bloodstream.
Where are drugs absorbed?
After oral administration of a drug, absorption into the bloodstream occurs in the stomach and intestine, which usually takes about one to six hours.
Is simple diffusion saturable?
Diffusion means that the net movement of particles (molecules) is from an area of high concentration to low concentration. If the particles can move through the lipid bilayer by simple diffusion, then nothing limits the number that can fit through the membrane.
Are passive transporters saturable?
Passive diffusion, therefore, requires no energy expenditure by the cell; it is not saturable or subject to competition between molecules.
What does saturable mean in biology?
One important characteristic that is associated with facilitated diffusion is saturation. This process is saturable, which means, as the concentration gradient of the substance increases, it will go on increasing until it reaches a point where all the carrier molecules are occupied.
What is saturable first pass metabolism?
The first pass effect (also known as first-pass metabolism or presystemic metabolism) is a phenomenon of drug metabolism whereby the concentration of a drug, specifically when administered orally, is greatly reduced before it reaches the systemic circulation.
Which route of drug administration has maximum bioavailability?
Drug in liquid form have more bioavailability than those of solids, while gases have the highest bioavailability. This is why inhalation is used in bronchial asthma.
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