Chapter 2 Flashcards
Pharmacokinetics
Drug movement through the body that is necessary to achieve drug action
Absorption, distribution, metabolism, and excretion
Absorption
Movement of drug into the blood stream after administration
Drugs taken by mouth
Disentigrate into small particles and then mix with a liquid (dissolution) to be absorbed by GI
Enter bloodstream following absorption across mucousal lining in small intestine. Dependent on villi
Fillers and inert substances (excipients)
Simple syrup, vegetable gums, aromatic powder, honey, elixirs
They increase the absorbality of the drug to make It a certain size
enteric coated drugs
Resist that gastric acid in stomach so It is absorbed in the small intestine
Should not be crushed
Passive transport
Diffusion and facilitated diffusion
Diffusion
High concentration to low
Facilitated diffusion
Carrier protein needed high-low
Active transport
Carrier protein low-high
Intramuscular absorption
Faster in muscles with increased blood flow
Subcutaneous generally has lower blood flow but are more rapid than by mouth
Rectal absorption
Slower than oral drugs.surface area in rectum is smaller
Absorption of oral drugs after GI
Intestinal lumen-liver-via hepatic portal vein-liver reduces amount of active drug (first pass effect)
Bioavailability
Percentage of available drug available for activity. Varies based on first-pass metabolism
Factors in bioavailability
Drug form Route Gastric mucosa and motility Administration with food and other drugs Changes in liver metabolism
Distribution
Movement of drug from circulation to body tissues
Influenced by rate of blood flow, drugs affinity to tissue, and protein binding
Protein binding
The portion of the drug that is bound to the protein is inactive because It cant interact with tissue receptors
Free drugs can exit blood vessels and reach their site of action
Highly bound protein drugs
More than 90% bound
2 highly protein-bound drugs are administered together, they compete for a binding site leading to an increase in free drugs. The higher the binding the more likely to bind.
Blood Brain Barrier
The BBB protects the brain from foreign substances. Blocks 98% of the drugs.
Drug metabolism
When the body chemically changes drugs into a form that can be excreted. LIVER.
Liver enzymes
Collectively referred to as the cytochrome P450 system, convert drugs to metabolites
Lipid soluble-water soluble substance for renal excretion. Some are transformed into active metabolites.
Drug half life
The drug half life is the time It takes for the amount of drug in the body to be reduced by half. The amount of drug administered, the amount of drug remaining in the body from previous doses, metabolism, and elimination affect the half-life of a drug.
Loading dose
A large initial dose that is significantly higher than maintenance dosing, therapeutic effects can be obtained while a steady state is reached
Drug excretion
Mainly through the kidneys. Excreted through bile, lungs, saliva, sweat, and breast milk
Urine pH influences drug excretion.
Pharmacodynamics
Is the study of the effects of drugs on the body
Dose-response relationship
Physiologicalresponse to changes in drug concentration at the site of action. Potency and maximal efficacy
Potency
Refers to the amount of drug needed to elicit a specific physiological response to a drug.
Therapeutic index
Which describes the relationship between the therapeutic dose of a drug and the toxic dose. Narrow therapeutic index needs to have close monitoring
Onset
Is the time It takes for a drug to reach the minimum effective concentration
Peak
Occurs when It reaches its highest concentration in the blood
Duration of action
Is the length of time the drug exerts a therapeutic effect
Therapeutic drug monitoring
Once steady state has been achieved, drug concentration can be determined by measuring peak and trough drug levels.
Peak drug level
Highest plasma concentration of drug at a specific time, and it indicates the rate of drug absorption.
Trough drug level
Lowest plasma concentration of a drug and It measures the rate at which the drug is eliminated.
Receptor theory
Drugs act by binding to receptors. Binding of the drug may activate a receptor, producing a response, or It may inactivate a receptor, blocking a response.
Receptors
Found on cell surface membranes or within the cell itself. Drug-binding sites are primarily on proteins, glycoproteins, prteolipids, and enzymes.
Cell membrane embedded enzymes
Ligand binding domain for drug binding is on the cell surface. The drug activates the enzyme inside the cell, and a response is initiated
Ligand-gated ion channels
Crosses the cell membrane. When the channel opens, ions flow into and out of the cells. Sodium and calcium ions
G-protein coupled receptors
Three components to this receptor responses are the receptor, G protein that binds with GTP and the effector, which is an ion or an ion channel
Transcription factors
Found in the cell nucleus on DNA, not on the surface.
Mechanisms of drug action
Stimulation Depression Irritation Replacement Cytotoxic action Anti criminal action And modification of immune status
Pharmacogenetics
Study of genetic factors that influence an individuals response to a specific drug. Genetic factors can alter drug metabolism, resulting in either enhanced or diminished drug response
Pharmecogenomics
Study of how genetics plays a role in the response to drugs
Phenocopy
An environmentally induced variation in an organism, c c loosely resembling a genetically determined trait
Phenotype
Observable physical or biochemical characteristics of an organism as determined by both genetic makeup and environmental influences
Polymorphism
The occurrence of different forms, stages, or types in individuals independent of sexual variations
Tachyphylaxis
Refers to an acute, rapid decrease in response to a drug.
Pharmacokinetics interactions
Changes that occur in the absorption, distribution, metabolism, and excretion of one or more drugs
Pharmacodynamic integrations
Result in additive, synergistic, or antagonistic drug effects
Additive effect
Sum of the two drug effects
Synergistic dug effects and potentiation
Both drugs together is greater than the effect of one drug alone
Antagonistic drug effect
One drug reduces or blocks the effect of the other
Drug nutrient interactions
MAOI (antidepressant) is taken with tyramine rich foods It causes hypertension
Drug induced photosensitivity
Skin reaction caused by exposure to sunlight
Photoallergic reaction and phototoxic
Photoallergic
When a drug undergoes activation in the skin by UV light compound that is more allergenic than the parent compound
Only requires previous exposure to light or sensitization to It
Phototoxic
Photochemical reactions within the skin to cause damage. Not immune mediated
Result of drug dose
