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24 Cards in this Set
- Front
- Back
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Passive Transport
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No energy required
diffusion |
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factors affecting diffusion
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concentration gradient- higher vs lower
drug properties: hydrophobic = lipophilic surface area of the cell - greater surface area = greater absorption |
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facilitated transport
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involves a carrier protein that facilitates the drug's transport through the cell membrane
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Active Transport
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Requires Energy
requires ATP as the energy source to fuel transport across the cell membrane |
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4 types of receptors
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Ligand-gated ion channels
G-protein receptors Enzyme-linked receptors Intracellular receptors |
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Ligand-Gated Ion Channels
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ion channels regulate the flow of ions into and out of the cell
common ions: Na, K, Cl, Ca allow the flow of ions in response to binging with a ligand/drug |
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Ligand
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anything that fits into a receptor
(a drug is a ligand) |
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G Protein-Coupled Receptors
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receptor spans the cell membrane
attached to a G-protein with 3 subunits: alpha, beta, gamma second messenger system (very specific types of proteins - structure) |
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second messenger system
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magnify the effect of initial activation, and create a cascade effect. This is generally the case with G-protein-coupled receptors. One G-protein can affect hundreds or thousands of proteins. This is known as amplification.
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Enzyme-Linked Receptors
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transmembrane receptor
receiving end outside the cell binds a ligand activating or enzyme activity on the portion of the receptor inside the cell. * involves an enzyme *may activate or inhibit an enzyme |
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Intracellular Receptors
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*binds on the inside
completely within the cytosol - receptor itself drug must be hydrophobic enough to pass through membrane (ie. steroid hormones) |
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Receptor Desensitization
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repeated activation or inhibition changes a receptor's responsiveness
tachyphylaxis receptor is desensitized and shows smaller effect of drug d/t neurotransmitter depletion down regulation: less synthesis of receptor because DNA not being transcribed as frequently Endocytosis: receptor degraded by lysosomes |
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Tachyphylaxis
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rapidly diminishing response to successive doses of a drug, rendering it less effective
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metabolism
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biotransformation of substances
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Metabolism in the Liver: 2 Phases
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phase 1 - converts a hydrophobic/lipophilic drug into more polar molecules
phase 2- the drug is conjugated by having a molecule added to it, making it more hydrophilic *both phases have distinct mechanisms of making substances more hydrophilic. Not all drugs need to go through both phases for elimination via the kidneys |
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Cytochrome P450
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metabolizes drugs in Phase 1
some drugs can inhibit this system. Some drugs can induce it. interactions are more common with strong inducers or inhibitors |
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Elimination
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primarily through Kidneys and urine
*the total body clearance of a drug is the sum of its parts: renal, hepatic, pulmonary and other methods. |
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Ion
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anything with a charge
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loading dose
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a large dose of a drug that rapidly increases plasma concentration of the drug. Once required concentration is achieved a different dose of the drug is continued.
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Therapeutic Index
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Ratio between toxic dose and therapeutic dose. The larger the number, the safer it is.
TI= TD50/ED50 |
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TD50
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amount that produces a toxic effect in 50% of the population
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ED50
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drug dose that produces a therapeutic effect in 50% of the population
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Therapeutic Margin/Window
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Expression of the TI as a measure of drug safety
a drug with a narrow margin may have significant toxicities when thrown out of its range. |
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Individual responses can throw a drug out of its range. Factors affecting this include:
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age
gender dietary changes other drugs being taken |
