Chapter 1 Flashcards
Systematic vs CNS Administration
Systematic: drug given in accordance to body weight
CNS: Given in terms of absolute amount (#of molecules/mole)
Dose response curves are in a _____scale
logarithmic
A Binary variable study will appear on a DRC as:
2 separate curves.
Formula for drug therapeutic index
TI= LD50/ED50
The higher the TI, the ____the drug
safer.
Efficacy
differences in MAXIMUM effect that drugs will produce at any dose.
Potentcy:
Differences in the ED50 of 2 drugs.
A drug with a LOW Ed50 has a ____ potency
high
ED50
MEDIAN EFFECTIVE DOSE-dose effective in 50% of the population
using a DRC, how can you tell if drug antagonism is occurring?
Drug antagonism: when the presence of one drug inhibits the affect of another
- can be seen if the DRC of a drug has shifted right (ED50 increased, need more drug to be effective) after the addition of another drug
Additive effect
When taking 2 drugs shifts the DRC curve to the left, decreasing the original effect
Superadditive effect
if the drugs together have a greater affect than intended
What is a parenteral route of administration
involves injection through the skin.
T/F Oil based vehicles speed up the rate of absorption
false, oil based vehicles slow the rate of absorption and allow the drugs effect to take place over several days.
4 main systemic parental routes of administration
1) subcutaneous
2) intramuscular
3) intraperitoneal
4) intravenous
Intrathecal injection
drug administered via injection into general nervous system.
Intracerebroventricular injection
injection directly into the brains ventricle system, gets injected into “aquaduct” and gets distributed throughout entire brain
Intracerebral injection
injection in which a drug is administered to a specific brain tissue.
Pros and Cons of Parenteral CNS administration
- not body weight dependent
- good for drugs that won’t trigger a response if injected into body (won’t pass blood brain barrier)
- good for molecules that are too big to reach the blood vessels in brain.
- not ideal because it involves drilling holes in skulls–> invasive.
2 Factors that effect the rate of absorption
1) increased blood volume near region of injection
2) heat
Drugs are absorbed into Bloodstream via _____ in the capillaries
pores in the capillaries.
Slowest method of parental injection… fastest?
subcutaneous, intravenous.
Depot injection
drug administered using oil based vehicle in the muscle to allow slow diffusion.
-drug needs to be oil soluble.
Why is inhalation of drugs more effective than per oral administration?
because with inhalation, less of the drug amount is subject to degradation by digestive enzymes and have the ability to get to the brain very quickly.
Difference between inhalation of gass and smoke (solids)
smoke particles and ask will not revaporize after it is dissolved in the lbood and therefore cannot be exhaled or eliminated via the respiratory system. smokes will thus collect in the lungs.
In intranasal administraition, drugs are sniffed into nostrils and absorbed via _____membranes
mucus membranes.
In oral administration, drugs are absorbed along GI tract, but the portion that does the absorbing in the mouth are the _____ membranes
buccal
Blood is collected from the blood vessels around the GI tract and delivered to the liver via the _____
hepatic portal system
Are ions and polar molecules lipid soluble?
no, they can therefore not cross the ion membrane without channels.
Percentage of drug ionization is dependent by:
mainly PKA ; the pH at which half its molecules are ionized
would a drug that is fully ionized in the digestive system be effective/
No, it won’t cross the membranes.
Ideal drug in reference to PKAs:
Bases with lower pKAs and acids with higher pKAs
Transdermal administration
absorbed through the skin
T/F A drug that is soluble in water would be effectively administered in transdermal administration
false. The skin is water resistant, it would be best if the drug was very lipid soluble.
Main factors affecting Drug distribution
1) Lipid Solubility; lipid soluble drugs will be easily absorbed but may get stored in the body fat and thus will take a long time to disperse
2) Ion trapping: injection of a non-lipid soluble drug (pka dependent) may make the drug slow to absorb
3) Blood Brain Barrier
4) Active and Passive transport
5) Protein Binding: drug may bind to large molecule that cannot fit through pore, limits distributions.
6) Placental barrier
What is the main part of the medulla that is not covered by the blood brain barrier? Why?
area postrema of medulla not covered by blood brain barrier because it triggers vomiting
Why is urine typically acidic?
because the kidneys mainly absorb things that are lipid soluble (they pass through the cell membrane) and selectively absorb ions via active and passive transports.
Acids are typically not reabsorbed into the blood because they are ionic, they tend to be retained in the urine.
Half life applies to a drug that has _____ Kinetics
first order
what is an example of a drug that does not follow a half-life curve
alcohol– it follows zero order kinetics.
Enzyme induction
levels of the enzyme go up in the body, usually because of a specific drug that uses that enzyme.
Example of enzyme induction
elevated levels of alcohol dehydrogenase in heavy drinkers.
What does Disulfiram do?
blocks ALDEHYDE dehydrogenase and prevents the breakdown of aldehyde into acetylcoA–> causes sickness
What does grapefruit juice to cytochrome enzyme?
affects FIRST PASS METABOLISM, and results in higher blood levels of many drugs.
