Exam1/ Lecture 2: Pharmacodynamics and Pharmacokinetics Flashcards
Lecture 1/22/23
What are the 5 reason why we need to know about pharmacodynamics and pharmacokinetics ?
- Produce onset of drug effect quickly
- Produce offset of drug effect quickly
- Severe consequences to “under” or “over” dosing
- Need to frequently adjust levels
- Low therapeutic index
Slide 2
Lecture 1/22/24
What is a receptor made of?
- Usually a protein
Slide 3
Lecture 1/22/24
What is a agonist
Activates receptor by binding to receptor
Lecture 1/22/24
What are the 3 bonds in agonist that is reversable
- Ion (or electrocovalent…oppositely charged ions)
- Hydrogen (to a very electronegative atom)
- Van der Waals interaction (the sum of attractive or repulsive forces; creates orbital shift)
Slide 4
Lecture 1/22/24
What are the 2 things that happen to the receptors once it is activated?
Conformational shape changes (Bound vs unbound)
Thermodynamically more/less active
Slide 3
Lecture 1/22/24
True or False: Drug effects is not effected by the number of bounds receptors.
False: Drug effect relates to number of bound receptors
Greatest effect….all receptors bound
Example: paralytics
Slide 3
Lecture 1/22/24
What is a antagonist
binds to a receptor but does not activate the receptor
Slide 5
Lecture 1/22/24
What are the reversible bond forces for an antagonist ?
3 reversible bond
- Ion
- Hydrogen
- Van der waals
Slide 5
Lecture 1/22/24
What type of antagonism, in large amounts progressively inhibits the agonist and shifts dose respone curve to the right?
Competitive antagonism
Slide 6
Lecture 1/22/24
What type of antagonism does not allow the agonist effects to happen regardless of how much agonist is given?
Non-competitive antagonism
Slide 6
Lectue 1/22/24
What type of agonist binds to a receptor casusing less response than the agoinst even at supramaximal dose?
Partial agonist
Slide 7
Lecture 1/22/24
What type of agonist compete for the same site as the agonist but produce the oppose effects?
Inverse agonist
Slide 7
Lecture 1/22/24
True or False: The number of receptors cannot increase or decrease depending on the comorbidity and drug therapy?
False, can increase or decrease depending on comorbidity, and drug therapy
Slide 10
Lecture 1/22/24
What are the 3 types of receptors?
- Lipid bilayer
- Intracellular proteins
- Circulating proteins
Slide 11
Lecture 1/ 22/24
What are 7 examples of lipid bilaryer receptors?
- Common for anesthesia drugs
- Membrane bound
- Opioids
- bzd
- b-blockers
- catecholamines
- nMbd
Slide 11
Lecture 1/22/24
What are 3 examples of Intracellular proteins receptors?
- Insulin
- steroids
- milrinone
slide 11
Lecture 1/22/24
What is an example of a circuating protein receptor?
anticoagulants
Slide 11
Lecture 1/22/24
Please label the graph:
* partial agonist
* inverse agonist
* full agoinist
* weak partial agonist
partial agonist - B.
inverse agonist - D.
full agoinist - A.
weak partial agonist- C.
Slide 8
Lecture 1/22/24
What does Renal Clearance involve?
Glomerular Filtration - GFR and amount of protein bound drug controls amount of drug entering tubule
Active Tubular Secretion - from peritubular capillaries, active transport process, penicillins
Passive Tubular Reabsorption - increased if drug is lipid soluble, ie thiopental, almost zero for water soluble drugs… excreted in urine
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1/22/24
What is Elimination 1/2 Time
time necessary to eliminate 50% of drug from PLASMA after bolus dose
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1/22/24
Time to a 50% decrease after infusion discontinued
(assumes a constant concentration, roughly relates to 1/2 life, increases the longer the infusion increases - accumulation in peripheral tissues)
Context Sensitive Half-Time
slide 27
1/22/24
what is Ionization
When the pk (dissociation constant) and ph are identical,
-50% of drug ionized, 50% of drug non-ionized
Most drugs are weak acids (Barbs) or weak bases (La and opioids)
-Acids are ionized in an alkaline ph/bases are ionized in an acid ph
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1/22/24
Characteristics of drug molecules
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1/22/24
how to figure out ionization vs non-ionization
Weak acids (barbiturates)
Pk after ph
Weak bases. (LA or opioids)
Pk before ph
So if a weak acid (pk 7.6) is put in a basic ph (blood 7.8)
7.8 – 7.6 = +0.2 acid drugs are ionized at basic ph
If weak base (pk 8.0) is put in an acid ph (Blood 7.2)
8.0 – 7.2= +0.8 weak bases are ionized at acid ph
“nicely negative numbers are nonionized”
slide 30
1/22/24
what is an Ion Trapping example
A pregnant lady gets a spinal anesthetic with LA and opioid (weak base, pk 7.3)
But fetal ph is lower than maternal ph (baby is in distress)
7.3 – 7.4 = -0.1 a bit non- ionized for mom
7.3 – 6.8 = +0.5 ionized for fetus and is trapped…. ”ion trapping”
In addition, the concentration gradient of non ionized drug to ionized drug for opioid is still higher in mom….
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1/22/24
what is:
“The sensitivity of the body to the drug”
“what the drug does to the body”
How do we figure this out?
Measure plasma concentrations at different pharmacologic responses….
Dopamine
Ie. Clinically, what are the drugs effects…
Pharmacodynamics
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1/22/24
What are causes for Individual Variability?
Elderly
-Decreased cardiac output…. To brain and liver….
-Decreased protein binding
-Increased body fat
Enzyme activity
-Acute vs chronic alcohol ingestion
Genetic disorders
-Atypical cholinesterase activity
-Malignant hyperthermia
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1/22/24
what is the difference between Potency vs Efficacy
Potency: concentration vs response….less drug with more effect = more potent
Efficacy: the ability of a drug to produce a clinical effect
slide 35
What is Relative Potency?
- Time to drug effect
- Plasma not the site of effect for anesthetic drugs
- Lag time between administration (plasma concentration) and effect
slide 36
What is Effective Dose (ED50) ?
Dose required to produce effect in 50% of patients
slide 37
What is Lethal Dose (LD50) ?
Dose required to produce death in 50% of patients
slide 37
What is Therapeutic Index?
- ratio between (LD50/ED50 )
- the wider/bigger it is, the safer the drug is and the the narrower it is, the more dangerous the drug is
slide 37
What is a Stereochemistry?
How drug molecules are structured In 3 dimensions
slide 38
What are Chiral Compounds?
- Molecules with asymmetric centers
usually related to way Carbon molecules are bonded. - the structure of an anti tumors and several of our popular drugs
slide 38
What are structural basis of Enantiomers?
- Chemically identical
- Mirror images
- Can’t be superimposed - not overlapping but like having but when my thumbs and my pinkies are on same sides.
slide 38
What is Dextrorotatory of an Enantiomer?
RIGHT rotation of light in a solution
slide 39
What is Levorotatory of an Enantiomer?
LEFT rotation of light in a solution
slide 39
What are the 2 drug sequences of Enantiomers?
- R: Rectus
- S: Sinister
slide 39
What is a Racemic?
- 50/50 mixture
- Optical activity equal
- Can exhibit different ADME
- One enantiomer is active; other inactive or side effects
- 1/3 of drugs
slide 39
What are examples of different Enantiomers?
- S-Ketamine = more potent with less delirium vs. R-Ketamine = like head injury effects of delirium
- L-Bupivicaine = less cardiac toxicity
- Cisatracurium = isomer of Atracurium that lacks Histamine effects
- Albuterol and Xopenex
slide 40
What is Pharmacogenetics/Pharmacogenomics?
How a single gene or all genes (genome) influences responses to drugs
slide 41
What is Pharmacogenetic Testing?
Look for variants in genes that code for:
* Drug-metabolizing enzymes
* Drug targets
* Immune proteins
slide 41
What does the acronym ADME stand for?
Absorption, Distribution, Metabolism, Excretion
Pharmacokinetics is the ________ study that details what the _______ does to the _____
Quantitative; Body; Drug
Pharmacokinetics determines the measurable concentration of the drug in the ______
Plasma
In a ONE compartment model, if a patient is hemorrhaging and a drug is administered, does the Volume of Distribution Increase or Decrease?
DEACREASE
What organs are considered part of a “Vessel Rich Group?”
Brain, Liver, Kidney
Is a one compartment volume distribution model accurate?
No
What are 4 common drugs that are taken up in 1st pass metabolism?
- Lidocaine
- Propranolol
- Meperidine
- Fentanyl (Includes SUfentanil and ALfentanil)
A HIGH Volume of Distribution of 5,000L indicates that a drug is ____ Soluble
Fat/Lipid
How does LOW plasma protein affect drug distribution?
Allows for more free, unbound drug to be available to cross cell membranes (Distribute through the body)
Acidic drugs primarily bind to what protein?
Albumin
Alkalotic drugs primarily bind to what protein?
A1- Acid Glycoprotein
Low plasma protein is commonly found in what patient demographics?
- ICU Patients
- Geriatrics
- Patients with Extended NPO time
- patients with Liver Cirrhosis Alcoholics
- Patients in Renal Failure
- Burn Patients
If a drug has a normal free fraction of 2%, what percentage is bound?
98%
(2% is available to go off and elicit desired clinical/physiological response
What drug (include its classification) is used as the gold standard to measure other drugs against?
Thiopental
It is a Barbiturate
If a drug is HIGHLY bound to plasma proteins, does it have a Large or Small volume of distribution? Give an example of one medication
Small Vd
Rx: Warfarin
The process of metabolism converts active, lipid soluble drugs to ____ soluble
Water
Why are many anesthetics lipid soluble?
The effector sites of the anesthetics are not in the plasma, they are in other parts of the body
Active Metabolites can have as high as ___% effect of the parent drug
50%
What process do Prodrugs require to become active?
PO Drugs must first be ingested but all Prodrugs require some form of early Metabolism
How are most drugs metabolized?
Hepatic Microsomal Enzymes ( the greatest)
Hoffman Elimination
Ester Hydrolysis
Kidneys
Tissue Esterase’s (GI Tract and Placenta)
Hofmann Elimination depends on what two physiological properties being within normal limits?
Temperature and pH
Hofmann Elimination is important in what types of drugs?
Neuromuscular Drugs
What 2 phases occur in Metabolism?
Phase 1: Increase polarity and prepare for Phase 2 reactions
Phase 2: Covalently link with highly polar molecule to become water soluble
What processes take place in Phase 1 metabolism?
Oxidation, Reduction, Hydrolysis
What process takes place in Phase 2 metabolism?
Conjugation
What gives the liver its red color?
A Heme cofactor
Where are the P450 enzymes located?
Attached to the Smooth Endoplasmic Reticulum of the hepatocytes
CYP450 absorbs what wavelength of UV light when exposed to Carbon Monoxide?
Wavelength 450nm
What is the most common enzyme in the CYP 450 family
CYP3a4, responsible for up to 60% of the CYP450 activity
Enzymatic INDUCTION leads to a(n) _______ in the amount of enzymes.
Increase
An induction of enzymes, _______ metabolism of a drug and requires _______ frequent dosing of a drug to reach desired clinical effect.
Increase; more
Enzymatic INHIBITION leads to a(n) _______ in the amount of enzymes
Decrease
Inhibition of enzymes, _______ metabolism of a drug and _______ the effects of the drug
Decreases; Prolongs
For most anesthetic drugs is constant so the Rate of clearance is proportional to ______
Concentration
What effects can be caused by the limited capacity of the liver to metabolize a drug
- Can lead to a buildup of a drug in the body, if the drug amount given exceeds the liver’s ability to metabolize