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20 Cards in this Set

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In most situations, it is necessary for the drug to get from the site of administration into the plasma (Absorption) and then to the desired site(s) of therapeutic action (Distribution) before?
a therapeutic benefit will be noted.
For all drugs, administration is followed by movement of the drug into the blood plasma is a process called?
Absorption.
Absorption includes?
movement of a drug into the blood: across the mucosa-lined epithelial surfaces of the lungs, gastrointestinal tract, nasal passages, and vagina, across the skin and the surface of the eye, and from injection sites (subcutaneous, intramuscular, and intraspinal).
A drug applied orally must cross the wall of the gastrointestinal tract and enter the plasma if it is to reach sites of action such as?
the heart, brain, and skeletal muscle.
A drug applied by inhalation with desired effects in the central nervous system must enter?
the plasma in order to reach the that site of action.
A drug applied on the skin for a desired effect at the site of administration will still be?
absorbed across the skin and enter the systemic circulation.
A drug which is inhaled (as an aerosol) in order to have effect on the bronchiole system will be?
still absorbed across the epithelium of this system and will enter the systemic circulation.
Absorption occurs regardless of?
whether or not absorption is actually required for the desired drug action.
What is required for absorption of a drug to occur?
Movement of Drug Molecules across cell membranes and across layers of cells
It's important to realize that the same processes by which drug molecules move across cell membranes and cell layers during absorption into the plasma from the site of administration are also important for movement of?
drug molecules out of the plasma in any tissue or organ, and for movement of drug molecules across cell membranes and cell layers within a tissue or organ.
Similarly, to be excreted from the body or to be metabolized, a drug must be?
removed from its site of action and be delivered in the plasma to sites of Metabolism and Excretion. (An exception to this idea: a very few drugs are metabolized in the plasma or at their site of action.)
At sites of metabolism and/or excretion, drug molecules must pass from?
the plasma into the extravascular space and either into the cells in which metabolism occurs or into the fluid medium in which the drug will be excreted. (Remember that some drug molecules maybe reabsorbed from that fluid medium back to the plasma.)
Whatever the direction of travel, drug molecules must?
move across cell membranes and across layers of cells.
Drug molecules may move across membranes and/or cell layers by three major mechanisms
Bulk Flow, Membrane Transporters, and Diffusion.
The rate at which drug molecules move from one body compartment to another (e.g., from the lumen of the gastrointestinal tract to the plasma, or from the plasma to the space surrounding cells within any particular tissue or organ) will be determined in part by the mechanism of movement.
However, regardless of the mechanism of movement, there are three major factors common to all three mechanisms of transmembrane and transcellular transport determining the rate of drug movement. These are?
Surface Area
Vascularization
Blood Flow
Absorption at a given site may be enhanced or reduced by?
alteration of the formulation of the drug.
As defined, absorption does not occur when?
a drug is applied by intravenous injection or infusion.
determining the rate of drug movement

surface area affects across which drug movement occurs –
the larger the surface area, the higher rate of movement (in terms of molecules per minute moving across the whole surface); think for example what would happen if the small intestine had a lesser surface area.
determining the rate of drug movement
vascularization of the surface across which drug movement (into or out of plasma) is occurring -
the higher the density of blood vessels, the higher rate of movement (in terms of molecules per minute moving across the whole surface); think for example what would happen if the small intestine had fewer blood vessels passing through it.
determining the rate of drug movement
blood flow "through" surface across which drug movement (into or out of plasma) is occurring –
the higher the perfusion of or blood flow through vessels, the higher rate of movement of drug molecules across the surface; think for example what would happen if blood flow through the small intestine was reduced.