Unit 1: Pharmacodynamics Flashcards Preview

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Flashcards in Unit 1: Pharmacodynamics Deck (41):
1

Pharmacodynamics

Focuses on the effects of drug on the body

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Agonists

Bind to and activate the receptor, turns on the response by mimicking an endogenous compound which the pt may be deficient

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Antagonists

Prevent binding of other molecules; blocks receptor in inactive site

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Prodrugs

completely reliant on biological processes for activation; genetics may prevent drug from reacting

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Bioavailabilty

fraction of unchanged drug found in circulation following administration

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Clearance

Rate of total elimination of drug divided by plasma drug concentration

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Volume of distribution

measure of the extent to which a drug is distributed in the body

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Pharmacokinetics

Focuses on the effects of the body on the drug

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Absorption

Movement of drug from the site of administration into circulation

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Distribution

Movement of drug from circulation to tissue, including receptor or active site

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Metabolism

Biotransformation of drugs into metabolites

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Excretion

Removal of unchanged drug and/or metabolites from the body

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7 types of transport

Bulk flow, filtration, passive diffusion, facilitated diffusion, active transport, endocytosis, ion pair transport

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6 Routes of administration

Enteral (epithelial), Inhalation (epithelial), mucous membranes (epithelial), parenteral (endothelial), transdermal, topical (epithelial)

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Epithelial absorption

Drugs must pass through the cells in the membrane, not between, so absorption is limited by the rates drugs can cross membrane

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First pass metabolism

term used for hepatic metabolism of a drug when it is absorbed from the stomach and delivered to the liver via portal circulation; Greater first-pass effect, less agent will reach systemic circulation

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Activated charcoal

Binds everything in the stomach and passes through

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Therapeutic window

Duration of action and concentration are in harmony; just enough drug to provide best reaction

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Highly/poorly perfused tissues

H: Brain, kidney, lungs, liver, heart P: Fat, distal extremities

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Volume of Distribution

A value given to a drug to indicate how well the drug is dispersed through the system; proportional to total drug in system/plasma concentration

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Influences of drug distribution

capillary permeability, lipid solubility, perfusion and protein binding

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Metabolism

Alters pharmacological activity of drug and increases ability of body to excrete drugs

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Phase 1 of metabolism

chemical modification; oxidation/reduction, hydrolysis etc

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Phase 2 of metabolism

Conjugation/ synthesis; enzymes serve to add large moieties that ionizes he molecule and drastically increases hydrophilicity... increases excretion

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Cytochrome P450

detoxification and bioactivation; oxidative reactions; primarily occurs in liver; over 60 enzymes

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Substrate

drug is subject to metabolism by enzyme

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Inducers

drug induces enzyme activity

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Inhibitors

drug inhibits enzyme activity

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Conjugation

adding a molecule to the drug to increase water solubility and increase subsequent excretion; usually decreases biological activity

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Factors that may effect metabolism

Smoking, age, sex, pregnancy, starvation, infection, circadian rhythm, CV, GI, renal or liver function, career, environment, drugs, alcohol, diet

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Routes of excretion

Renal (90%), liver, intestines, lung, sweat, saliva, breast milk

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3 major mechanisms of excretion

Glomerular filtration, tubular secretion, passive reabsorption

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Glomerular filtration

Occurs in Bowman's capsule, dominated by bulk flow filtration, rate is driven by hydrostatic pressure, size dependent

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Tubular secretion

Active transport of large molecules or protein bound molecules FROM plasma TO urine across epithelial cells; can move molecules across concentration gradient; can be saturated or inhibited

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Reabsorption

Molecules moving FROM urine To plasma, mediated by diffusion; small, neutral and lipophilic molecules are reabsorbed

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Biliary drug excretion

hepatocytes actively secrete bile, flows to duodenum and eliminated; several drugs are secreted this way

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Breast milk excretion

Lipid soluble, non-ionizable molecules freely dissociate in breast milk

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Zero-order kinetics

Excretion not at all dependent on drug concentration; few drugs behave this way: alcohol; no fixed half life; clearance is constant

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First-order kinetics

Excretions is HIGHLY dependent on drug concentration; fixed half life; exponential elimination

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Cockcroft-gault equation

most common equation used to measure creatinine release based on age, sex, weight

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Child-pugh score

used to adjust meds based on hepatic clearance