Lecture 8-Pharmacology Flashcards
Exam 1
Pharmacokinetics (PK)
- “movement” of drugs
- How the body acts on drugs
Pharmacodynamics (PD)
- “Power” of drugs
- How drugs act on the body
“PK” is described by ADME(T)
- Absorption
- Distribution
- Metabolism
- Elimination/Excretion
- Toxicity
All of these factors are influenced by body weight (dose and body fluid)
Common forms of administration
- Oral
- Inhalation
- Transdermal
- Intranasal
- Sublingual (via mucous membanes)
- Injection- intravenous, subcutaneous, Intramuscular, Intraperitoneally
- Lumbar puncture and epidural
- Rectal
- Devices (infusion pumps and IUDs)
Oral administration
- Drug must be soluble and stable in stomach fluid (not all drugs can handle stomach environment)
- Food in stomach will slow down “passing” which means delayed absorption and decreased maximum drug level achieved
- About 75% absorbed in 2-3 hours which is slow
Advantages of oral administration
- safest
- easiest to give measured, specific does bc of premade amounts
- slow absorption process
Disadvantages of Oral Administration
- slow absorption
- Occasional vomiting/stomach distress
- Unpredictable absorption rate (based on food in stomach)
- Some drugs are destroyed by stomach acid
caveat: crushing tablets- consider dangers and alternate routes
Inhalation
- Probably the 2nd most popular method
- faster than oral as the first organ blood leaving the lungs goes to is the brain
Transdermal (skin patches) how do they work?
- Works as patch has contact adhesive, drug reservior, and a drug releasing membrane
Advantages and disadvantages of transdermal administration
- alternative to oral (no gastro side-effects)
- increased penetration at sites with greater cutaneous blood flow
- Extended release
Disadvantages: skin is a strong barrier so the drug must be able to penetrate the skin
Sublingual administration
- Through mucous membranes (esp mouth bc lots of blood vessels and a mucuous membrane there)
- Is fast acting (efficient and quick absorption)
- Doesn’t irritate stomach or cause vomiting
Limitation: unpleasant tast of drugs- not used much (but good for people who can’t swallow)
Injection advantage and disadvantages
- Advantage: one of the fasted absorption rates depending on type
- Dis: “sterile” conditions necessary, danger of too much drug administration, painful
Subcutaneous vs Intravenous vs Intramuscular
- Subcutaneous: under the skin
- IV: into vein (directly into the bloodstream)
- IM: directly into muscle
Distribution
T/F: Once absorbed, a drug is distributed primarily to the site of its’ primary action
- FALSE
- Once absorbed, a drug is distributed ALL OVER the body by circulation of blood, not just at the site of action
Two concepts about absorption from the blood-brain
- Lipid solubility
- Drugs that are lipophilic (like lipids aka fat) take much longer to reach site of action
- Marijuana and alcohol are lipophilic which means the drug can linger and stay in fats, solvent that can adgere to fat and is why alcoholics get fatty liver
Two concepts ab absorption from the blood-brain
The Blood Brain Barrier (BBB)
- Not an actual wall but a structural concept, provides a gatekeeper function (can choose what gets in and out)
- Psychoactive drugs must penetrate the BBB to reach sites of action
- Some drugs can diffuse through the BBB
Endothelial cells (capilaries) and astrocytes (glial cells)
Metabolism
- liver and kidneys chemically change drugs so they can be excreted
- To become deactivated, a drug must: be excreted from the body AND/OR be chemically changed
How does drug metabolism happen?
- Liver breaks down circulating drugs, and the metabolites (chemically changed drug/byproduct) are then carried in the bloodstream to the kidneys
- In the kidneys that metabolites might remain in the urin for excretion
- first pass-metabolism!
Enzymes role in metabolism?
- Enzymes are proteins that break down/metabolize drugs
- Specialty enzymes in the liver are called liver microsomal enzymes
- They lack specificity- also break down toxins in food and environmental pollutants!
