Clinical pharmacokinetics and pharmacodynamics of stereo isomeric drugs
PHARMACOLOGY CH. 5 Pharmacokinetics. Pharmacokinetics explained… How the body handles the drugs...
Transcript of PHARMACOLOGY CH. 5 Pharmacokinetics. Pharmacokinetics explained… How the body handles the drugs...
PHARMACOLOGY CH. 5
Pharmacokinetics
Pharmacokinetics explained…
How the body handles the drugs that are administered to it, how the drugs are changed from the original form into something that the body can use and how they are secreted from the body and eliminated.
Plasma Concentration
Once absorption is complete, the level and concentration of the drug in the body is the plasma concentration
The affinity of a drug effects plasma concentration
The bloodstream is the “vehicle” which will deliver the drug to the parts of the body where the drug will have an effect
Drug Absorption
How the drug enters the bodyDependent on the type of drug, how it is designed
and the reason for the use.Liquids are more readily absorbed than tablets or
capsules because they are already “broken down”Cell membranes contain both lipids and proteinsThis makes them semi-permeable; allows and
prevents the entrance and exit of materials.Other than IV and intra-arterial(straight into the
bloodstream), a certain amount of time is required before they start to work in the body
Absorption cont.
Absorption does not always go by way of the stomach to the blood stream.
Example= InhalationsAlso rectal and vaginal medications are very
slow release rates; they are considered topical applications
Topical medications are not necessarily absorbed through the skin into the bloodstream
Absorption
Injections by-pass the absorption phase-results are achieved quicker
Inhalations enter the bloodstream via the alveoli
Rectal and vaginal administrations are considered topical and have the slowest rate of absorption
Drug Distribution
Using the circulatory system (heart and bloodstream), the body distributed the molecules
Some drugs bind to plasma proteinsSome drugs “float” through the bloodstream
and interact with receptors
Membrane Transport Mechanisms
The way in which drugs get from outside of the cell into the cell
Diffusion
Passive Diffusion-across the cell membrane. -is another term for passive transport The force that permits the substance to be
transported from outside the cell into the cell depends on the concentration difference
Generally, move from high to low concentration
Facilitated Diffusion- carrier protein permits molecules to pass through the certain parts of the cell
Active Transport
Costs the cell energyAlso uses a concentration gradient to move
substances into and out of the cell
Pinocytosis
Cell engulfs the substance, thereby allowing the substance to enter the cell
Most drugs and foods are absorbed at a much faster rate in the small intestines than in the stomach.
Solubility
The more lipid-soluble the drug, the faster the drug will be absorbed into the cell
The PDR( Physician’s Desk Reference) defines drugs in terms of their chemical structure; also brief descriptions of drugs make up including drug solubility
For a drug to be absorbed via the gastrointestinal tract, the drug must be both water and lipid soluble
Ionization
The charge of a moleculeBioavailability is what?If a chemical is ionized, it will not readily
cross the cell membrane barrierUn- ionized drugs are more readily absorbed
into the cell
SSRI
More Antidepressants