Lecture 2 Flashcards
PPT 1 and 2
What happens when a drug binds and gets stuck to a receptor?
A covalent bond is formed; becomes insurmountable
Drugs continuously bind and _____ to the receptor
Release
What does Duration of drug action refer to?
How long the drug will bind to the receptor
What happens when a receptor becomes insurmountable?
A process called desensitization; the cell degrades the receptor shutting down the signaling process. It is a protective mechanism for the cell
What makes a good receptor?
-Increased selectivity: binds to 1 drug or 1 drug type
-Alteration: In order for the downstream effect to occur, the receptor has to be altered after the drug binds.
What makes a bad receptor?
-No alteration: “inert binding sites” No detectable change in function after binding therefore the drug has no effect on the body
- Non-selective: Bind to just any drugs
What is the most important plasma protein?
Albumin
Describe Albumin.
Large and doesn’t cross barriers easily; when bound to drugs the drugs also cannot cross barriers.
What are Drug Carriers?
They are used to get drugs where they need to go
When can a drug cross a barrier?
When it is in its free form it can diffuse into tissue and bind to receptors
What can affect the levels of albumin in the body? What happens to drugs in the body when this happens?
-Malnutrition, liver damage Kidney failure
-The amount of free drug in the CVS will increase d/t not having enough of albumin to bind to. You will see increased effects, increased toxicity and increased negative side effects.
Albumin bound is ______. Receptor bound is ______.
Bad
Good
What drug is highly bound to albumin?
Phenytoin
What drug competes for binding sites with phenytoin? What is the result of this?
-Carbamazepine (another anti-seizure)
-Because of this you will see an increased concentration of free drug of both of these drugs
What are the 3 drug carriers?
Albumin
Alpha-1 glycoprotein
Lipoproteins
What type of drug does Albumin mostly bind to?
Acidic drugs
What type of drug does Alpha-1 glycoproteins mostly bind to?
Basic drugs
What type of drugs does Lipoproteins mostly bind to?
Neutral drugs
What is the definition of drug concentration?
The amount of drug in the plasma
What is the definition of drug dose?
How much I gave the patient (think of how the concentration would differ if you give PO vs IV even though it is the same dose)
What is potency?
Concentration (EC50) or dose (ED50) of a drug required to produce 50% of that drugs maximal effect. The greater the effect at 50% = higher potency
What is maximal efficacy?
It is the most important!
It is the max response a drug can deliver; varies per drug
What does the maximal efficacy depend on?
Drug interaction with the receptor
Although maximal efficacy is most important, what should you take into account?
DRUG TOXICITY
Think: Although this drug has a high maximal efficacy, what toxic side effect will I see at that max response? What dose/concentration will I have to give the patient to see these results? Will the benefits outweigh the risks?
The larger the therapeutic index, the ______ the drug
Safer
What is the Median Effective Dose (ED50)?
Where 50% of the population will see effectiveness of a given dose
What is the Median Toxic Dose (TD50)?
Where 50% of the population will see toxic side effects at a given dose
What is the Median Lethal Dose (LD50)?
It is not used in humans!!
Where 50% of the population will have lethal side effects
What does the therapeutic index do?
Establishes the margin of safety
ED50 vs TD50
Shows effectiveness vs toxicity
In animals, how do you find the therapeutic index?
LD50 / ED50
In humans, how do you find the therapeutic index?
TD50 / ED50
What does a narrow therapeutic index indicate? Give an example
That the dose is more toxic. Need to monitor closely. A very small increase in dose could have negative SE
Digoxin; warfarin; lithium
What does a wide therapeutic index indicate? Give an example
That the drug is safer. Small increases in drugs are less likely to have negative SE.
Ibuprofen; Tylenol; Antihistamines
What has an affect on drug responsiveness?
Polypharmacy (Drug-drug interactions); genetic factors; idiosyncratic (usual drug response with no reason why; maybe genetics); tolerance; tachyphylaxis; chemical antagonist; physiologic antagonism
What is tolerance? Give an example
The response decrease over the course of therapy; needing a higher dose for previous response.
-Morphine
What does tachyphylaxis mean?
Developing a quick tolerance
How does a chemical antagonist attribute to drug responsiveness in a patient?
If a patient is taking another drug that is binding to the same receptor that we need for another drug that we are giving, we will see decreased results.
What factors can cause an alteration in the concentration of a drug in the body?
The rate of absorption, distribution, and clearance can be affected by age, weight, sex, disease state (liver/kidney failure)
How does the endogenous ligand effect drug responsiveness?
The endogenous ligand may be affected by your health. This can cause less or more of the endogenous ligand to bind to receptors that are meant to be bound to a drug we are giving. If it’s less of the endogenous ligand then the effect of the drug will increase. if it’s more, then the effect of the drug will decrease.
How does the function or number of receptors effect drug responsiveness?
The more functional receptors you have, you will see an expected response from the drug.
If you have less receptors or receptors that are not functional;, then you’ll see less of a response of the drug.
How does the alteration of the receptor affect drug responsiveness?
This refers to the downstream response of the receptor. This is the largest and most important cause of variation in drug responsiveness referred to as “post receptor process”; if there is no alteration then there is no downstream effect therefore decreasing drug responsiveness.
What is an example of a drug that has both desired and adverse side effects at the same receptor? Example?
Recemic mixtures
Esketamine and R-ketamine.
A drug needs to be _______ to cross barriers?
Uncharged
Can drugs with small charges cross barriers?
Yes.
Why do drugs need to mostly be uncharged to cross barriers?
The inner cell wall is hydrophobic (uncharged) then the drug should be too so it can cross easily. The uncharged drug can go through the polar head (charged) portion on the cell wall fine.
What is a weak acid?
pH below 7.5
Releases H+ into solution (-)
What is a weak base?
pH above 7.5
Absorbs H+ from solution (+)
What is pKa?
Dissociation constant
What does the Henderson Hasselbach Equation do?
It relates pH to pKa and vice versa
if pH < pKa then
favors protonated form
Has [H+] attached
if pH > pKa then
favors unprotonated form
No [H+] attached - not attached.
Why is protonated vs non protonated important?
Protonated has a harder time crossing barriers
In a weak acid, the pH < pKa…
protonated; uncharged