Principle Concepts Flashcards
Therapeutic Range
Plasma concentration at which a drug exerts its desired effect
Dosage Regimen
●The amount, route, frequency, and duration of drug administration
●Determines the amount of drug being administered to an animal, based on:
1. Dose
2. Dosage interval
Route of Administration
●Drugs must be administered in a form and by a route that will allow them to reach their target site in the body
–Topical
–Oral
–Inhalation
–Parenteral
Pharmacokinetics
Sequence of events that occur once a drug is administered
1. Drug Absorption: Drug is absorbed into the bloodstream
2. Drug Distribution: After absorption there is distribution to body fluids and tissues, including target tissue
3. Drug Metabolism: The body begins to break down (metabolism)
4. Drug Elimination: excrete the drug immediately after absorption
Define: Drug Absorption
●Movement of drug from administration site into systemic circulation
Define: Bioavailability
degree to which drug is absorbed and reaches systemic circulation
Hydrophilic
(ionized) molecules that diffuse through the fluid that is between cells
Lipophilic
non-ionized molecules that diffuse across the cellular membrane
Define: Drug Form
Solid drug forms must be broken down to smaller particles before absorption therefore delaying absorption
Drug Distribution
●Once in the systemic circulation drug must be distributed to target tissues
●Initial distribution is to highly perfused tissue such as the brain/vital organs
●Drugs enter target tissue at capillary level
The “rights” of proper drug administration:
• Right drug
• Right dose
• Right route
• Right time
• Right patient
• Right documentation
Define: Dose
amount of drug administered at one time
Define: Loading dose
initial dose of drug given to get the drug concentration up to therapeutic range in a short period of time
Define: Maintenance dose
the dose of drug that maintains or keeps the drug at therapeutic levels.
Pharmacokinetics includes?
- Drug Absorption
- Drug Distribution
- Drug Metabolism
- Drug Elimination
Drug Absorption is affected by?
Affected by
route of administration
drug’s hydrophilic/lipophilic nature
drug form
GI tract condition
Liver metabolism after GI absorption
Blood perfusion at administration site
Polarity affects a drug molecules ability to move across physical barriers
◦ Greatly affected by the PH of the body
Hydrophilic can be given?
SQ
Lipophilic can be given?
PO
the First Pass Effect
Some drugs can be completely metabolized by the liver which stops the drug from reaching the heart and other body tissues.
Example: Diazepam (Seizure med) - This is why its given IV so it will go straight to the heart & than to the brain and does not get completely absorbed by the liver.
• Blood Perfusion at the Injection Site
◦ This essentially means if you inject in the same location multiple times than the skin will begin to scar therefore decreasing blood flow
Drug Distribution refers to?
• Once in the systemic circulation drug must be distributed to target tissues which are the highly perfused/vascular tissues/organs:
target tissues are?
◦ Brain, Heart, Lungs, all visceral organs (Abdominal organs), muscle, & last the skin
Drugs can enter target tissue at the?
capillary levels
Blood Brain Barrier
◦ Central Nervous System has specialized capillaries that do not allow protein bound drug molecules through
◦ Prostate, Eyes & Placenta have these specialized capillaries as well.
Drug Distribution is highly affected by?
the hydration status of the animal
metabolism is?
the body’s ability to change a drug chemically from the form in which it was administered into a form that can be eliminated from the body.
Another name for biotransformation is?
Metabolism
Most biotransformation occurs in the?
liver
Why does metabolism occur in the liver?
because of the action of microsomal enzymes called cytochrome P450 enzymes found in liver cells.
cytochrome P450 enzymes
found in liver cells. These enzymes induce chemical reactions that change the drug chemically to allow elimination in the urine or bile.
Once a drug has been biotransformed, it is called a?
metabolite
what are the four chemical reactions that are induced by microsomal enzymes in the liver to biotransform drugs?
- Oxidation—loss of electrons
- Reduction—gain of electrons
- Hydrolysis—splitting of the drug molecule and addition of a water molecule to each of the split portions
- Conjugation—the addition of glucuronic acid or similar compounds to the drug molecule; when these compounds are attached to a drug molecule, the drug becomes much more water soluble
Removal of a drug from the body occurs at
the kidney and at the liver.
competitive inhibition
is when 2 drugs are metabolized by the same enzyme, 1 drug will overwhelm the system so the other drug is metabolized slower therefore it goes past the therapeutic range causing it to be toxic.
Enzyme induction
is when there is 2 drugs are metabolized by the same enzyme and 1 drug is metabolized faster than the other so it won’t reach the therapeutic range
Removal of a drug from the body occurs at which organ?
Liver & Kidney
Drug elimination rate are dependent on?
A drugs half life
Poor what flow can lead to toxicity?
Renal Blood Flow
Drugs half life is used to determine?
Dosage interval & withdrawl time
A longer drug half life means it takes longer or shorter to eliminate from the body?
Longer
Drugs must be combined with what to exert their effect?
Cellular receptors
What are cellular receptors?
Body tissues have specific cellular receptors that match drug receptors allowing the drug to bind with the tissue and exert their effect
Agonist Reaction refers to?
a drug delivering the therapeutic effect of the desired drug in the most efficient manner
Atongist means?
No desired drug action - blocking the receptors
Nonrecptor Drugs is called?
Mediated Drug Effect
explain Mediated Drug Effect
Some drugs are able to fulfill there therapeutic duties without bringing to cellular receptors
examples of drugs that have Mediated Drug Effect
EDTA, Mannitol & antacids
how does EDTA work?
EDTA binds to calcium to prevent a clot from forming so it’s not taking binging to specific cellular receptor
how does antacids work?
they contain calcium & magnesium which bind to the stomach acid to neutralize it and prevent ulcer formations
