What is pharmacokinetics?
the study of how a body deals with a drug (what the body does to the drug)
What are the components of pharmacokinects?
1) A - Administration
2) D - Distribution
3) M - Metabolism
4) E - Elimination
What are the two divisions of administration?
1. Alimentary "Enteral" "GI System - take by mouth and absorbed by gut before it gets into your system
2. Non-Alimentary "Parenteral" - things like inhalation, injection, or transdermal
What is the primary goal of taking a drug?
to get enough of that medication into your system to create the desired effect
Why are drugs considered NOT very "selective"?
Attach to receptors on cells that have nothing to do with the desired response (certain part of the drug is lost there too)
What is duration of action?
the amount of time drug is above the therapeutic level
What is the typical and extended relief duration of action?
Typical - 6 hours
Extended rel - 8-12 hours
What is the #1 advantage of oral medications?
ease and convenience
Why is it helpful for enteral administration to be absorbed in the small intestine (2 reasons)?
1. The large surface area to take advantage with absorption
2. Allows a fairly consistent rate into the circulation, which increases the safety of the drug
What factors affect absorption?
1. Ability to disintegrate the drug and dissolve into ions (then absorbed thru the membrane)
2. Motility of the GI tract
(T/F) It is useful for the drug to move quickly thru the stomach.
True (faster into bloodstream)
(T/F) It is useful for the drug to move quickly thru the GI tract.
False; drug will be moved along too quickly before it has a chance to be absorbed
The mucus membrane enzymes of the GI tract breakdown some of the drug and make it not as useful to the body. Because of this, doctor's will prescribe more of the dose to get through this
- Smoking increases the activity of these enzymes, so a greater amount of drug will be metabolized. So the net effect of smoking is (increased/decreased)?
i think decreased
Drugs can be absorbed best in a ________ state.
If a drug is acidic, it passes thru the stomach (readily/slowly).
How can you defer absorption from the stomach until the gut?
What are 5 disadvantages of taking medications orally?
1. For a drug to be absorbed by the gut it needs to be lipid soluble so it can diffuse passively (all drugs can't be lipid soluble)
2. To diffuse readily it should remain in a non-ionized state
3. First-pass effect - Passing by the liver by portal vein before it goes into the general circulation; lose up to 50% of the effective dose at the first pass
4. Visceral blood flow - Affected by things such as age, comorbidites (alter how much is in system)
5. There are some things they can combine to (antibiotic + milk) that makes it totally ineffective
What two types of ingestion are considered their own category?
1.) Sublingual - putting a tablet under the tongue and just letting it dissolve (oral by mouth but different absorbed thru oral mucosa to superior vena cava) that goes directly to heart and distributes thru body (totally miss first pass effect)
2.) Rectal - can be used for someone who is very ill and can't swallow (maybe intubated or vomiting a lot)
§ Negative is poor absorption and tissue irritability (lower GI tract not designed to absorb)
□ Not used often but can be used in special situations
3 advantages of Parenteral "non-alimentary"?
1. Generally allows more drug to target site
2. Better predictability of the amount of drug delivered
3. Usually misses the first pass effect
What is the advantage of inhalation?
rapid onset (quick, effective absorption)
because of large surface area between alveoli and capillary bed
Why does a general anesthetic provide such a rapid response?
Alveolar side - simple squamous epithelial (both sides)
Capillary - Endothelium (one cell layer thick - fused basement membrane)
only one cell thick - very quick
What are three types of injections?
1. IV - direct line into vascular system
- 100% of drug in vascular system (won't lose any to the liver)
Positive - Well vascularized - drugs to get into the system well (eventually)
Negative - Painful - Anything that affects circulation to the muscle can change absorption rate (exercise right after injection and really pump up muscle you'll really affect the absorption rate)
3. Subcutaneous injection "sub-Q