8/26 Class 2 Flashcards
What dictates the duration of drug action?
- only as long as the drug binds to the receptor (because of constituent activity)
- long term downstream effects last until downstream effectors go away (when downstream is used up)
- Covalent bonds (receptor is desensitized or degraded. (think g protein))
Good receptor properties:
- selective- drug binds to a single receptor or receptor type
- alteration- a drug binds and the receptor changes to create a downstream effect
Bad receptor properties:
Drug carriers. They bind to the drug and carry them places, but when it’s done, it won’t have any effect on the body
The part of the drug that is not bound to a carrier is said to be in it’s
free form
What is the most important drug carrier?
albumin
When a plasma protein is bound to a drug, that drug (can or cannot) cross ______.
Why?
cannot cross barriers
the protein is too large
What partially dictates whether a drug is bound or not?
It’s charge and how it interacts with a particular carrier protein
When can a drug cross barriers?
when it is in it’s free form
What can a drug bind to that will effect how much of a drug we have to give?
plasma protein binding.
The more bound to protein the less that’s usable to bind to receptors.
Giving phenytoin to a malnourished patient will have what effect?
A higher effect. Because they don’t have as much albumin for the drug to bind to.
What are inert binding sites?
A carrier in the blood- it doesn’t elicit a response.
What are the 3 types of carrier receptors?
Albumin
alpha 1 acid glycoprotein
lipoproteins
What type of drug does albumin bind to?
acidic drugs
What type of drugs does alpha 1 acid glycoproteins bind to?
basic drugs
what type of drugs to lipoproteins bind to?
neutral drugs
Define potency
concentration or dose of a drug required to produce 50% of that drugs maximal effect.
what is the maximal efficacy?
Greatest possible response a dose can deliver
Describe the Potency of drug A, B, C, and D.
Drug B is very potent because it’s 50% response only takes a small drug dose.
Drug A, C, and D each have less and less potency, because it takes more and more the drug to reach it’s 50% response.
Which drug(s) has the highest efficacy?
A,C,D
The larger the therapeutic index, the ______
safer the drug
What is the therapeutic index?
a margin of safety between the effectiveness of a dose vs the toxic dose for 50% of the population (studied).
What is the therapeutic index ratio?
What type of drugs have a wide therapeutic index?
OTC drugs
What is the ED50?
median effective dose on 50% of a population studied.
What is an idiosyncratic response?
A unusual drug response (we don’t know the reason behind it)
What causes idiosyncratic responses?
Genetic factors
What is tolerance?
When a person changes their response to a drug over time.
Need more and more morphine
What is tachyphylaxis?
quick tolerance
What are the 4 causes of variation in drug responsiveness?
- Alteration in concentration of drug that actually reaches the receptor.
i.e. age, weight, sex, disease state - variation in concentration of endogenous receptor ligand (not every person has the same amount of receptors. Disease can change this)
- alteration in number of function of receptors (native ligand binding to receptors and using them all up so none are left for the drug)
- Changes in components of response distal to receptor. (the downstream effect)
What is the largest and most important cause of variation in drug response?
Changes in components of response distal to receptor. (downstream effect)
Can a drug cause desired and toxic effects at the same receptor?
yes. i.e. racemic mixtures
In order to cross barriers effectively, drugs should be_______
uncharged