Exam 1 Flashcards
ADME, Pharmacogenomics
What is pharmacology?
The study of the properties of drugs and their interactions with the living system.
What is pharmacodynamics?
“What drugs do to the body”. Relationship between drug concentration and biologic effects with time.
What is pharmacokinetics?
“What the body does to the drug”. The absorption, distribution, metabolism, and excretion of the drug.
Explain dosing in relation to the bell curve.
Dosing of a drug was given to represent the 68% of people within 1 standard deviation of the bell curve. However, not all individuals can be helped by the dosing strategy.
Why was the original style of dosing initially founded?
It was thought to be more cost-effective as manufacturing an individual dose is not. It was also thought that the optimal drug dose can only be determined empirically (through observation).
What are the different factors that influence an individual’s response to a medication?
Environment
Diet
Age
Lifestyle
State of health
What is pharmacogenetics?
Pharmacogenetics is the study or clinical testing of genetic variations that give rise to differing responses to drugs. Individual gene concept.
What is pharmacogenomics?
Pharmacogenomics is the study of how an individual’s genetic inheritance affects the whole body response to drugs. Whole genome concept.
What is the promise of pharmacogenetics/ genomics?
Will allow for effective drugs to be tailor made for a person’s genetic makeup. It will allow for maximum efficacy and minimum toxicity. It will also prevent adverse effects caused by ineffective and toxic drugs for that person.
How has molecular medicine impacted drug administration?
Molecular medicine has allowed us to move from trial and error treatment to targeting a specific pathogenic defect. It has allowed us to design drugs better instead of solely moving chemical groups around. It has also allowed us to predict efficacy and toxicity of drugs in individuals.
What was the example given for the start of pharmacogenetics?
Succinylcholine was used as a muscle relaxer in schizophrenic patients. It should be metabolized in minutes and patients should wake up. Small population did not wake up and it was found that there was a polymorphism in the enzyme that breaks down the drug. The result was that these patients needed to be on mechanical ventilation for longer.
What are microarrays used for?
They are used to look at the up-regulation and down-regulation of RNA. For example, how does RNA expression look different in those who respond to a certain drug and those who do not respond to that drug?
What is pharmaceutical biotechnology?
Biotechnology refers to the application of biological systems, living organisms, or their derivatives in making or modifying products of processes for specific use. It is used to manufacture drugs, pharmacogenomics, gene therapy, and genetic testing.
What is a biomarker?
A biomarker is an indicator for a disease state. Biomarkers must be actionable and impact patient care decisions to be clinically relevant.
What is absorption?
Transfer of a drug from the site of admin to systemic circulation (blood).
What is distribution?
Transfer of a drug from systemic circulation (blood) to the tissues.
What is elimination?
Removal of drug from the body
What are the 3 factors that determine the absorption of a drug?
- Route of administration (oral, IV, IM, etc)
- Chemical properties
- formulation
What is enteral administration?
Oral, sublingual, rectal
What is parenteral administration?
IV, IM, SubQ
What are the advantages of enteral admin?
Safe
Economical
Convenient
What are the disadvantages of enteral admin?
Limited absorption (destroyed by digestive enzymes and low pH in stomach)
Irregularities in absorption due to competition with food
Emesis due to gastric irritation
Metabolized by 1st pass effect
What is the first pass effect?
Oral drugs exposed to liver first are metabolized before reaching systemic circulation.
What are exceptions to first pass effect?
Sublingual, rectal, IV, IM, SubQ
What are the advantages of parenteral administration?
Better regulated with more predictable absorption (no 1st pass)
More accurately select effective dose.
What are the disadvantages of parenteral admin?
Risk of infection
Pain with injection
Difficulties with self-medication
What area of absorption has the largest surface area?
Small intestine
(mouth and stomach are small with large intestine being bigger)
What are the 9 factors that modify absorption throughout the GIT?
- Solubilization of drug
- Formulation factors
- Concentration of drug at absorption site
- Blood flow at absorption site
- Surface area of absorption
- Gastric emptying
- Food
- Intestinal motility
- Metabolism of drug by GIT
What is the definition of drug solubilization?
Drug solubilization is the breaking down of drugs into smaller more absorbable particles.
What are formulation factors?
Formulation factors are materials added to a drug during processing that can affect the solubilization of the drug. Includes fillers, disintegrators, binders, and lubricants.
How does the concentration of the drug at the site of absorption modify the rates of absorption?
The driving force of absorption across membranes is the concentration gradient. The higher the concentration of the drug, the faster the rate of absorption.
How does the flow of blood at absorption sites modify the rates of absorption?
Blood flow at sites of absorption maintain the concentration gradient. As blood continues to flow, there is continually more drug in GIT and less in blood allowing this process to continue until all drug enters systemic circulation.
How does the surface area of the GIT modify the rates of absorption?
More surface area= more room for things to be absorbed into blood
What is the primary site for drug absorption?
Small intestine
How does gastric emptying modify drug absorption?
Anything that delays gastric emptying (fatty foods) will decrease drug absorption.
Anything that accelerates gastric emptying will increase drug absorption. This is applicable for all drugs.
How does intestinal motility modify absorption of drugs?
If a drug is not completely absorbed before entering small intestine, increasing intestine motility will slow down rates of absorption. Decreasing intestinal motility will increase the rates of absorption.
How do metabolic enzymes within the GIT modify drug absorption?
Proteases in GIT break down peptides and microbes in GIT can metabolize certain drugs. Microbes can activate or deactivate drugs
What properties of drugs allow them to be permeable to the epithilum?
Small (O2, CO2, H2O)
Hydrophobic/ lipophilic (polarity)
What properties of drugs inhibit them from being permeable to the epithilum?
Large and charged (glucose, metallic ions).
In a very general sense, how do hydrophilic molecules pass into the cell?
Paracellular diffusion
In a very general sense, how to lipophilic molecules pass into the cell?
Transcellular diffusion
What are the 4 types of drug transport?
- Passive diffusion (electrolytes and non-electrolytes
- Filtration
- Carrier-mediated transport (active and facilitated)
- Recepter-mediated endocytosis
What is the most common form of movement for drugs?
Passive diffusion
What is Kp?
Kp is the lipid-water partition coefficient.
Kp= Conc. of drug in lipid phase/ Conc. of drug in aqueous phase
What is the driving force of passive diffusion?
Concentration gradient
What are the characteristics of passive diffusion?
Low molecular weighted drugs.
Hydrophilic and lipophilic both.
Driving force is the concentration gradient.
A low Kp indicates…
More soluble in water. Molecule is more hydrophilic.
(Katie is LOW on water)
A high Kp indicates…
More soluble in lipid. Molecule is more lipophilic
(Katie is HIGH on fatty foods)
What is the weak acid equation?
HA ——–> H+ + A-
The unionized form (HA, the acid) is the favorable form for absorption. Being uncharged is like being lipophilic.
Why is passive diffusion of electrolytes more complicated?
Electrolytes ionize within solutions. They become either weak acids or weak bases.
Does a higher Kp allow for faster rates of absorption?
Yes. A higher Kp indicates a more fat-soluble (lipophilic) drug molecule therefore it can cross membranes at a faster rate to enter systemic circulation.
What is the weak base equation?
BH+ ——> B + H+
The unionized form (B, the base) is the favorable form for absorption. Being uncharged is like being lipophilic.
What is pKa?
pKa is the pH at which half of the molecules are in the ionized/ charged form (water soluble) and half the molecules are in the unionized/ uncharged (Fat soluble) form.
What is the henderson-hasselbalch equation?
In general, the uncharged/ unionized form of weak acids (HA) and weak bases (B) are …
Lipophilic
In general, the charged/ ionized form of weak acids (A-) and weak bases (BH+) are…
hydrophilic
When the pH of the solution is LESS than the pKa of the drug, what form of the weak acid dominates?
unionized/ uncharged weak acid
(HA)
(phu less than pkkaaa, i know your acid is uncharged)
When the pH of the solution is LESS than the pKa of the drug, what form of the weak base dominates?
ionized/charged weak base (BH+)
When the pH of the solution is GREATER than the pKa of the drug, what form of the weak acid dominates?
ionized/charged weak acid (A-)
When the pH of the solution is GREATER than the pKa of the drug, what form of the weak base dominates?
unionized/uncharged weak base (B)
What is the driving force of filtration?
Pressure gradient and size of molecule relative to pore (small passes while large is held back)
What is filtration in terms of drug transport?
Filtration is the transfer of drugs across a membrane through pores or through spaces between a cell. (Capillary endothelial membranes and renal glomerulus)
Lipid soluble molecules typically undergo ___________ for drug transport.
Passive diffusion
Water soluble molecules typically undergo ___________ for drug transport.
Filtration
What are the 6 characteristics of carrier-mediated ACTIVE transport?
- Transports important large molecules (sugars, AA, etc)
- Carrier or receptor-mediated
- Selective for certain drugs
- ATP!!!
- One-way process
- Inhibition is possible!!
What are the 5 characteristics of carrier-mediated FACILITATED diffusion?
- Carrier or receptor-mediated
- Selective for certain drugs
- Saturation is possible
- NO ATP!!!
- Two-way process (reversible)
What are the differences between facilitated diffusion and active transport?
Active transport requires ATP, is a 1-way process and can be inhibited. Passive diffusion does not require ATP, is bi-directional, and can be saturated.
What is receptor-mediated endocytosis?
This is when drugs (hormones, GFs, antibodies, etc) bind receptors on the cell surface in coated pits and then the ligand and receptor are internalized and form endosomes.
What is bioavailability?
Bioavailability is the fraction of the administered drug that actually reaches systemic circulation.
Amount of drug that is not metabolized by 1st pass metabolism.
(100mg of drug given orally and 60 reaches systemic circulation. Oral bioavailability is 60%)
How can bioavailability be calculated?
(AUC oral/ AUC IV) x100
What is bioequivalence?
A measurement of comparison between drugs. Bioequivalence is a measure between two drugs in the areas of max conc. of drug and extent of drug absorption.
How is the concentration of a drug calculated?
Concentration= Mass (mg)/ Volume of solution
Volume meaning drug in solution, in blood, or in plasma
What are the 4 factors that effect drug distribution?
- Blood flow
- Capillary permeability
- Transfer rate from interstitial fluid into tissues
- Binding of plasma proteins
What areas of the body have the highest perfusion rate?
Perfusion rate is the ratio of blood flow to tissue mass. The highest perfusion rates are in the heart, kidney, liver, lungs, and brain.
How does regional blood flow affect drug distribution?
The greater the blood flow to a certain tissue, the more rapid distribution of drug from plasma into interstitial fluid.
A drug will appear in the interstitial fluid of the highest perfusion tissues (heart, brain, kidney, liver, etc) _________ than it appears in the lowest perfused tissues (skin, muscle).
Faster
Through what process do drugs pass through capillaries?
Filtration
(remember: in filtration, hydrophobic molecules undergo passive transcellular diffusion while hydrophilic drugs needs to use the fenestra for paracellular diffusion)
How does capillary permeability affect drug distribution?
Large capillary fenestra allow for a greater filtration potential like in the liver. Small capillary fenestra means a lower filtration potential like in the brain.
Where is the interstitial fluid?
Interstitial fluid is surrounding the cells and blood vessels.
How is drug distribution affected by plasma proteins?
Plasma proteins bind and hold onto the drug therefore keeping in is systemic circulation longer.
When drugs are bound to plasma proteins, they are in there _________ state.
Inactive (no receptor reached, not distributed, not metabolized, not excreted)
What are the 3 main types of plasma proteins?
- Albumin
- Lipoproteins
- Alpha1-acid glycoproteins
What type of drugs does albumin typically bind to?
Weak acids and hydrophobic drugs
What types of drugs do lipoproteins typically bind to?
Hydrophobic drugs.
What type of plasma lipoprotein has the strongest binding ability?
VLDL>LDL>HDL
How is a patient with good HDL levels affected in terms of drug distribution?
A patient with good HDL levels has less drug binding with HDL allowing drugs to be more efficacious and leave systemic circulation faster.
What type of drug do alpha1-acid glycoproteins bind to?
Basic drugs.
________ plasma proteins = ________ free drug available
MORE
LESS
The placenta is another barrier present in the body like the BBB. What characteristics of the placenta make it much less effective as a barrier?
High in fat content and highly perfused. Molecules less than 600 MW cross barrier easily.
What is the apparent volume of distribution?
The apparent volume of distribution is the theoretical volume of fluid into which the total drug administered would have to be diluted to produce the concentration in the plasma.
In simple terms, it is how readily or not the drug will remain in systemic circulation or redistribute to other tissues.
What is the volume of distribution equation?
Vd= Dose/ Plasma concentration at time zero
What percentage of total body water (interstitial, intracellular, plasma) does plasma make up?
around 4%
What does a low volume of distribution mean?
LOW Vd = drug likely to stay in systemic circulation or bound to plasma proteins
What is the main purpose of metabolism?
The main goal of metabolism is to increase the hydrophilicity so that it can be secreted in the urine.
Metabolism can increase, decrease, or not change the overall __________ and ___________ of a drug.
Toxicity and activity
What are the 3 types of drugs metabolism?
Phase I/II metabolism
Phase III metabolism
What are the main organs that metabolize drugs?
Liver, kidney, and intestines
Basic drugs have a ________ volume of distribution.
High. Basic drugs will go to the tissues
Acidic drugs have a _________ volume of distribution.
Low. Acidic drugs will stay in the blood.
Metabolism is based on the basic characteristics of what?
(this is the stupid one that compares biotransformation to metabolism)
- Structural change
- Emphasis in the outcome
- Focused on applied science
In phase I and II metabolism, what is happening to the drug?
Structural change through the addition of chemical groups.
Inside the organelles, where is phase I and II metabolism occuring?
In the microsome (ER) and cytosol. Not in the plasma membrane
Inside the organelles, where is phase III metabolism occuring?
Abundantly occurs in the plasma membrane but can occur in the microsome (ER).
Are there any hydrophilicity changes to the drug in phase III metabolism?
No, this all occurs during phase I and II.
Which phase of metabolism increases hydrophilicity the most?
Phase II increases hydrophilicity the most. The exceptions occur in methylation and acetylation.
(methylation and acetylation are decreasing polarity meaning they are becoming more lipophilic)
Which phase of metabolism involves the crossing of cell membranes?
Phase III
Which phase of metabolism involves hydrolysis, reduction, and oxidation?
Phase I
What are the enzymes involved in phase I hydrolysis?
Carboxylesterases
Cholinesterases
Epoxide Hydrolases
Peptidases
What is the function of carboxylesterases in phase I metabolism?
Carboxylesterases hydrolyze esters, thioesters, and amides.
CES1- cleaves unbound compounds
CES2- cleaves bound compounds
What is the function of cholinesterases in phase I metabolism?
Colinesterases hydrolyze esters.
What is the function of epoxide hydrolases in phase I metabolism?
Epoxide hydrolases hydrolyze epoxides.
What is the function of peptidases in phase I metabolism?
Peptidases hydrolyze amides.
In phase I metabolism, reduction is a relatively minor pathway. What are the two types changes in reduction that turn 1 molecules into 2?
Addition of an Azo group (N=N) and disulfide groups (S-S). Overall reduction adds an H atom.
In phase I metabolism, oxidation is the most common type of change. What percentage of molecules undergo oxidation as their form of phase I metabolism?
90%
Does oxidation require cofactors?
Yes, oxidation of molecules in phase I metabolism requires cofactors. They include NAD, FAD, and molybdenum.
What are the 7 enzymes that participate in oxidation reactions in phase I metabolism?
- Alcohol dehydrogenase
- Aldehyde dehydrogenase
- Aldehyde oxidase
- Xanthine oxidase
- Monoamine oxidase
- CYPs
- FMOs
(Oxidation includes the +oxygen or the -hydrogen)
What are the two most important enzymes in phase I oxidation?
CYPs and FMOs
Do CYPs or FMOs have more functional genes?
CYPs (57 functional) have more overall and functional genes compared to FMOs (5 functional)
What is the prosthetic group (molecules needed in order for the enzyme to function) in CYPs?
Heme-Fe
What is the prosthetic group in FMOs?
FAD
What is the affinity and capacity of CYPs?
CYPs have high affinity but low capacity.
What is the affinity and capacity of FMOs?
FMOs have low affinity but higher capacity.
What is 1-aminobenzotriazole?
This is a substance used in lab work to knock out CYPs in order to see if CYPs or FMOs metabolize a drug.
What are the 2 FMO types involved in disease development?
FMO3 and FMO5
Which FMO is the most broad?
FMO1
Why are CYPs called CYP450?
CYPs are called CYP450 because when it is attached to CO, spectroscopy absorbs it at a wavelength of 450.
What are the 4 characteristics of CYP450s?
- Absorbed at 450 wavelength
- Catalytic cycle
- Slow (catalytic cycles are slow)
- Reductase involved
What percentage of drugs are metabolized by CYP3?
50%
What are phase II reactions?
Phase II reactions are conjugation reactions. Included addition of acetyl groups, methyl groups, glucuronic groups, glutathione groups, and sulfo groups.
What is the most abundant enzyme in phase II metabolism?
- UGTs (UDP glucuronosyl-transferases)
- GSTs (glutathione S-transferases) and SULTs (sulfotransferases)
What is the purpose of methylation in phase II metabolism?
Goal of methylation is to decrease the polarity of the drug molecule.
What is the donor molecule for methylation in phase II metabolism?
S-adenosylmethionine (SAM)
What are the major enzymes that function in methylation for phase II metabolism?
N- O- S-
methyltransferases
What is the purpose of acetylation in phase II metabolism?
The goal of acetylation is to decrease the polarity of the drug molecule and increase transporter affinity.
What are the majors enzymes that act in acetylation in phase II metabolism?
NAT1 and NAT2
What are the two drug examples that undergo acetylation in phase II metabolism?
Sulfamethoxazole and Isoniazid
What is the donor molecule for acetylation in phase II metabolism?
Coenzyme A
What is the purpose of glutathione conjugation in phase II metabolism?
The purpose of glutathione conjugation is to increase polarity and transporter affinity. Drug molecules that undergo glutathione conjugation are very hydrophilic to start.
What is the donor molecule for glutathione conjugation in phase II metabolism?
Glutathione
What is the major enzyme that participates in glutathione conjugation in phase II metabolism?
GST
What are the two examples of drugs that undergo glutathione conjugation?
Acetaminophen and Cisplatin
What is the major pathway in phase II metabolism?
Glutathione conjugation
What is the purpose of sulfation in phase II metabolism?
The purpose of sulfation is to increase polarity greatly. Drug molecules that undergo sulfation are very hydrophilic to start.
What is the donor molecule for sulfation in phase II metabolism?
PAPs
What is the major enzyme that participates in sulfation in phase II metabolism?
Sulfotransferases (these have a higher affinity than UGTs)
What are the two drug examples that undergo sulfation in phase II metabolism?
Acetaminophen and Estrone
What is the purpose of glucuronidation in phase II metabolism?
The purpose of glucuronidation is to increased the polarity of the drug molecule and increase capacity.
What is the donor molecule in glucuronidation in phase II metabolism?
UDPGA
What is the enzyme that participates in glucuronidation in phase II metabolism?
UDP glucuronosyl-transferases (UGTs)
What are the two examples of drugs that undergo glucuronidation in phase II metabolism?
Chloramphenicol and Valproate
Phase II reactions in general favor excretion of the drug by _____________ affinities towards transports which can be done by increasing, decreasing, or not changing the lipophilicity of the drug molecule.
INCREASING
What are the two example drugs that undergo methylation in phase II metabolism?
Azathioprine and Apigenin
What is phase III metabolism all about?
Phase III metabolism is about membrane-transport. It requires energy and moves against concentration gradients.