Readings Chapter 1 Flashcards
What is a critical point when trying to define what a drug is?
The intention of the drug used
Routes of administration involving injection through the skin into various parts of the body, using a hollow needle and syringe.
Parenteral route
What is the liquid called that the drug is suspended or dissolved in before it is injected?
a Vehicle
What is the most common vehicle?
Normal/physiological saline 0.9% sodium chloride in water.
What are the four common parenteral routes?
- subcutaneous
- intramuscular
- intraperitoneal
- intravenous
An injection just under the skin.
subcutaneous
What is the popular term for intravenous injection?
Mainlining
What is the term for a tube that is surgically implanted into the body for when i.v injections are necessary.
When are these often used?
Catheter
Often used to study self-administration of drugs by animals.
Term for when the needle is inserted into the nervous system between the base of the skull and the first vertebra.
Intrathecal
Wiki: used for spinal anaesthesia, chemo, pain management
An injection directly into one of the brain’s ventricles.
Intracerebroventricular
What type of injection would you consider performing (instead of an intracerebroventricular) to more precisely determine drug effects on specific areas?
Intracerebral
A rigid tube resembling a hypodermic needle. Often used when pereforming intracerebral injections.
A cannula
How do injected drugs pass through the pores of a capillary?
By diffusion (moving from an area of high concentration to an area of low concentration until they are equal in both areas)
Why do intraperitoneal and intramuscular injections absorb more rapidly than subcutaneous?
B/c muscles and the peritoneum have access to more capillaries
When a drug is dissolved in high concentration in a oil which is then injected into a muscle (usually the bum).
The drug is then slowly diffused from the oil into the body fluids over a long period of time. (can be up to 4 weeks)
Also: What is a type of drug that would be administered using this method?
Depot injections.
Antipsychotic medications because people do not like to take them and don’t continue to use them after being released from the hospital.
For a depot injection to work best, what type of drug must it be?
Highly lipid soluble- otherwise they would be released too quickly
What is the principle that governs the movement from inhaled air into the blood and vis versa?
Why is this so useful?
Diffusion
Useful b/c the drug passes out of the blood into the air and is exhaled so that the concentration of the gas in the blood reflects the concentration in the gas that is breathed. Allows controlling the control of drug in the blood with precision. (why anesthesia is done with gas)
What is a ‘positive’ of heating refined drugs until they vaporize and inhaling them?
No smoke is involved, and therefore no hydrocarbons or carbon monoxide.
Powdered drugs such as cocaine, heroin and tobacco snuff are sometimes sniffed into the nostrils. This is known as ______ or ______
Intranasal administration or
Insufflation
How is chewing tobacco absorbed?
Through the buccal membranes (mucous membranes)
If someone is unconscious or vomiting, what is a useful way of administering medication?
Intrarectal
Where is a drug absorbed most efficiently?
In the intestines
How can we test lipid solubility of a drug?
Using the olive oil partition coefficient
Equal amounts of olive oil and water are placed in a beaker, and a fixed amount of drug is mixed in. The oil and water are separated and the amount of drug dissolved in each one is measured.
Drugs that are highly lipid soluble are more highly concentrated in the oil and poorly lipid-soluble drugs will end up in the water.
This will somewhat predict the degree to which a drug will dissolve in fat tissue in the body.
When does a molecule lose its ability to dissolve in lipids?
When it’s charged. (An ion)
Ions cannot pass through membranes.
When drugs are absorbed through the skin
Transdermal administration
What type of substances can pass through the epidermis? (In other words, what type of drugs can be administered transdermally?)
Lipid-soluble substances
Where will you find highly lipid soluble fats concentrate in the body? What is the outcome of this?
Highly lipid soluble drugs tend to stay in lipids wherever they encounter them (eg. outside of the CNS in the body). Few drugs have any effect in body fat, and is inactive. The fat acts as a sponge and prevent lipid-soluble drugs to getting to their SOA. The drug is later released into the blood slowly over time.
Special cells in the CNS that wrap themselves around the capillaries and block the pores through which substances normally diffuse. Provides a solid lipid barrier so that non-lipid-soluble substances have a great difficulty getting in the brain.
Blood-brain barrier
What is the difference between passive transportation and active transportation?
Active uses energy and passive doesn’t
What are the two passive transport mechanisms?
- Large protein molecule may create a channel that allows non-lipid soluble molecule to pass through in response to diffusion.
- Non-lipid soluble molecule attaches to a carrier protein that permits it to diffuse across the membrane.
When drugs are concerned, what is the term for the metabolism?
Detoxification
The process of reconstructing molecules? What is the product?
Metabolism
Metabolites
Any drug absorbed from the digestive system will pass through the liver, and therefore a certain about of metabolism, before going anywhere else in the body.
First-pass metabolism (Also includes metabolism that is done in the stomach and intestines)
Are all drugs subject to first-pass metabolism?
No! Only ones that have gone through the digestive tract.
What is the rate of excretion for must drugs?
Half life
How do the kidneys and liver interact?
kidneys excrete molecules of unwanted substances of the metabolism from the liver.
What does first-order kinetics look like on a graph? Why?
It is an asymptote. This is because it occurs when a drug is eliminated in terms of a half-life (eg 50% of the original blood level is eliminated in 30mins, 25% of the original level 30mins later etc.)
Most drug excretion can be described in terms of a half-life, except one drug. Which one?
Alcohol
When the rate of elimination of a drug is a straight line, it is said to have ___________.
Zero order kinetics
it will be a set speed eg 15mg/10ml of blood/hour
Levels of a given enzyme can be increased by previous exposure to a specific drug that uses that enzyme or some other enzyme site. This is responsible for the development of metabolic tolerance.
Enzyme induction
The effects of a drug change over time during a single administration. This change reflects increasing and decreasing drug levels after administration. When plotted on a graph, what is the result usually called?
Time course
A range of doses that produces therapeutic response without causing any significant adverse effect in patients. If drug reaches too high of a level, there will be unwanted side effects, and no increase in therapeutic effect. If drug falls below certain level, it will not have a therapeutic effect at all.
Therapeutic window
How do you keep a drug to stay within it’s therapeutic window?
It must be taken at the correct dose at regular intervals
What is an example of a drug that is absorbed and excreted rapidly, making it hard for it to be kept within it’s therapeutic window?
Lithium (used for BPD)
In research papers, how are doses for drugs usually reported?
Milligrams per kilogram of body weight
eg 6.5mg/kg
Generally, do small or large animals higher metabolic rates? What does this mean?
In general, smaller organisms have higher metabolic rates and so drugs are metabolized faster, so research done on rats and mice often seem ridiculously high in human terms
What data should be presented in a dose response curve?
- A dose so low that there is no detectable effect
- A dose so high that increases in dose have no further effect
- A number of doses in between
What does ED50 represent in a dose-response curve?
The median effective dose where the dose is effective in 50% of the individuals tested (ED99 would be the does that is effective in 99% of all cases)
What does LD50 represent in a dose-response curve?
The median lethal dose where 50% of the individuals died (LD1 is the dose that kills 1% of it’s subjects)
What is the term that is used to describe the safety of a drug? How is it determined?
The therapeutic ratio is TI=LD50/ED50 . The higher the TI, the safer the drug
When you are comparing 2 drugs that have the same effect ______ refers to the difference in the ED50 of the two drugs.
Potency. The drug with the lower ED50 is more potent.
______ refers to differences in the maximum effect that drugs will produce at any dose.
Effectiveness
What are two ‘types’ of effects a drug has?
The primary/main effect is the one the drug is taken to produce. Any other effect is a side effect.
If one drug diminishes the effect of another, this interaction is called _______.
Antagonism
What will you see when you draw a DRC of two drugs where there is antagonism between them? What are the two DRCs representing?
One DRC will be drawn for the drug alone and a second DRC for the drug in the presence of the other drug.
If the DRC of the first drug is shifted to the right (ED50 increases) by the addition of the second drug, this indicates antagonism between the drugs
One DRC will be drawn for the drug alone and a second DRC for the drug in the presence of the other drug. What is the effect if the DRC shifts to the left?
The ED50 decreases, the drugs have an additive effect.
What exists if drugs have an effect together that is greater than you would expect by simply combining their effects?
A superadditive effect or potentiation exists.
When is it clear if a drug interaction is addictive or superaddictive?
If one drug has no effect alone, but increases the effect of a drug, potentiation/a superadditive effect is occuring
