Principles Of Pharmacology (4,5) Flashcards
Pharmacokinetics
What the body does to the drug
Pharmacodynamics
What the drug does to the body
Does the statement “how drug concentration in the plasma changes over time” refer to pharmacokinetics or pharmacodynamics?
Pharmacokinetics
-change in concentration = what the body is doing
Does the statement “relationship between drug concentration and effect” refer to pharmacokinetics or pharmacodynamics?
Pharmacodynamics
-what the drug is doing and how that is related to concentration
ADME stands for
Absorption, distribution, metabolism, elimination
Pharmacokinetics can be broken down into
ADME
Pharmacokinetics (how drug concentration i the plasma changes over time) provides information relevant to
-how long it takes to work
-route administered
-dose and dosing interval
Absorption
Movement of administration site into the molecules/bloodstream
What is the importance of drug administration
-affects how quickly and how much of drug is entering circulation
-not all routes are suitable for all drugs
Drugs are administered as a formulation depending on
- Route
- Time for course of action
- Active drug concentration
Enteral administration
Entry of drug through the GI tract
-absorption takes place somewhere between mouth and anus
Parenteral administration
Done not by the GI tract
-any other administration
-usually injection
PO stands for
Swallowing
Oral administration (PO)
Usually drug absorbed via stomach/small intestine
-absorption is <100%
Oral absorption depends on
-solubility/disintegration
-acidity of GI tract
-stability of drug
-gastric emptying and motility
-GI blood flow
Benefits of oral administration
Easiest, safest and cheapest
-drug doesn’t need to be sterile or pure (acid/protective measures)
Drawbacks of oral administration
-acid sensitive, protein drugs are unstable
-pt needs to be conscious and cooperative
-variable absorption
-possible GI irritability
First pass metabolism effect
Most drugs given orally first pass through the liver before entering the systemic circulation
What is the problem with first pass metabolism effect?
There is a chance that the drug molecules in the blood enters the hepatic portal vein and is absorbed into liver cells, being metabolized which creates a risk for a portion of the drug being changed
-drug concentration can drop dramatically
Extent of drug metabolism is
Drug to drug dependant
-depends on what drug is being used
If there is extensive first pass metabolism what will need to be prescribed?
There will need to be additional doses prescribed
-for example, if only 15% of the drug is not metabolized by the liver, then there will need to be additional doses as only 15% is surviving
Rectal administration (pr)
Absorption through rectal mucosa
Benefits of rectal administration
-rapid
-cheap and easy
-good if you can’t swallow
-less first pass effect
(pr) stands for
Per rectum
Drawbacks of rectal administration
-absorption can be incomplete
-many drugs cause irritation of mucosal lining
Sublingual (SL) administration
Drug placed under the tongue, where it dissolves into mucosa under tongue
Advantages of sublingual administration (SL)
-rapid absorption
-no fast pass effect (usually why it is SL)
-suitable for acid sensitive drugs
-fast, easy, cheap
Disadvantages for sublingual administration
Many drugs taste bad
Pharmacokinetic profile is more in common with
SC, IM, IV administration
Capsules
Powder in a gelatin coating
-allows for faster absorption
Buccal film
Tablet that just sits in the gum area
Subcutaneous injection (SC)
Drug is injected under the skin into subcutaneous tissue
Advantages of Subcutaneous injection (SC)
-rapid as it enters general circulation
-local drug delivery
-easy self administration
Disadvantages Subcutaneous injection (SC)
-requires sterile drug
-personal preference
-absorption relies on blood flow and injection volume
Intramuscular injection (IM)
Drug injected into skeletal muscle
Advantages for Intramuscular injection (IM)
-can be in large muscle mass
-self administration
-systemic circulation absorption can be controlled (oil based formulation)
Disadvantages for Intramuscular injection (IM)
Can be painful
Intravenous (IV)
Drug injected directly into vein
Two types of Intravenous (IV)
-rapid bolus (IV push)
-continuous infusion (IV drip)
Advantages of Intravenous (IV)
-all drug enters bloodstream (100% bioavilibity)
-rapid distribution and onset of action
-can have large drug volumes
Disadvantages for Intravenous (IV)
-requires skilled administration and close monitoring
-drug must be sterile
-greater cost
Inhalation
Drug inhaled into airways
Advantages of inhalation
-Useful for local action but can be absorbed into pulmonary circulation
-no first pass effect
-useful for gasses
Disadvantages of inhalation
-limited absorption of large proteins
-possible irritation of lung lining
Formulations for inhalations
Can be gasses or gas mixtures
Inhalers for pulmonary use are made up of
-particulate powders
-nebulized (mist)
Pressurized aerosol and other containers allow for
Unused product to remain uncontaminted for later use
Topical routes
-skin
-eyes
-nose
-vagina
Transdermal
Aborsption thorugh skin
-for local and systemic effects
Benefits of transdermal
Cheap and easy
-simple local administration
-no first pass effect
Drawbacks of transdermal
Not suitable for many drugs (fat insoluable)
-absorption affected by skin hydration