OMSI- FAMM III

polymorphisms

genetic variations

how can genetic variants effect drug metabolism?

can effect rate of metabolism by 4-6 fold. Effects number of receptors possible for the drug, and the amount of enzyme possible to metabolize that drug to be excreted.

ultrarapid metabolizer

• increaes enzyme activity

• has 2 increased function alleles or more

• CYP2C19×17/*17

• CYP2D6×1/*1xN

Rapid metabolizer

• increased enzyme activity

• a combination of normal and increased function alleles

• CYP2C19*/*17

Normal metabolizer

• fully functional enzyme activity

• Combination of normal allels

• CYP219*1/*1

Intermediate metabolizer

• decreased enzyme activity

• combinations of normal and decreased/no function alleles

• CYP219×1/*2

Poor metabolizer

• little/no enzyme activity

• either no/decreased function alleles

• CYP2C19×2/*2

CYP2D6

• converts codine to morphine in the body to create a pain releiving effect.

• Ultrametabolisers have many of these enzymes, which can lead to excessive morphine in blood stream. Overdose possible

CYP2C19

• metabolizes many important drugs: Clopidogrel, propranolol, Omeprazole, diazepam, tricyclic antidepressants

• Clopidogrel cannot be activated without this enzyme

• loss of function means less drug is bioavailable

• gain of function means too much antiplatelet activity, risk of excessive bleeding.

Dihydropyrimidine dehydrogenase (DPD)

• metabolizes 5-FU ( a chemo drug for colorectal cancer)

• loss of function will cause a slower elimination of 5-FU, higher risk of toxicity. Can cause bone marrow supression

Warfarin metabolsism: CYP2C9 and VKORC1

• CYP2C9 deactivates S-warfarin, the more potent form

• VKORC1 is inhibited by warfarin to cause anticoagulation

• Loss of function CYP2C9 causes slow metabolism, risk of toxicity

• Loss of function VKORC1 has less target for warfarin, more free in blood, risk of toxicity

UGT1A1

• detoxifies and clears SN-38, the metaboliste of irinotecan (chemo drug for colorectal cancer)

• loss of function: active metaboliste accumulates, can cause bone marrow suppression and sever diarrhea. Gilbert syndrome

atypical pseudocholine esterase

• caused by loss of function of the enzyme that metabolizes certain neuromuscular blocking agents

• Ex. Succinylcholine, meant to cause temporary paralysis during surgical procedures. With this condition, it can take much longer to clear. Can cause respiratory paralysis.

hydroxylase polymorphisms

• an enzyme that metabolizes certain drugs

• ex. phenytoin is not metabolized fast enough in loss of function cases. This can cause a plamsa buildup, which even mildly can cause death

Acetylator status

describes how quickly your body processes certain medications

• determined by N-acetyltransferase activity (NAT)

• rapid acetylators metabolize certain drugs faster

• slow acetylators metaolize certain drugs slower, increasing exposre

• ex. isoniazid (TB drug), a slow metabolism can inhibit pyridoxine kinase and cause less B6 in the body. Increases pt risk of peripheral sensory neuropathy. fast metabolism causes buildup of acetyhydrazine, which can damamge liver

thiopurine S-methyltransferase (TPMT)

• inactivates several chemotherapy drugs and immune supressents

• loss of function causes accumulation of thiopurine metabolites, which can cause bone marrow supression

Glucose-6-phosphate dehydrogenase deficiency

• an enzyme in PPP, regenerates NADPH is cells to maintain glutathione (antioxidant) levels.

• people with G6PD deficency, when exposed to oxidizing drugs, their RBC become stressed and can die (acute hemoysis)

HLA polymophisms

cause varients in immune responses to certain drugs.

• For example, HLA-B 57*:01 vareint can cause abacavir (Ant-HIV) immune reaction

organic anion transporter (OATP) 1B1 transpoeter

• transporter in liver cells, moves several drugs into liver from bloodstream. ex. statins

• loss of function: less drug enters liver, more in bloodstream. higher risk toxicity. ex. statins can cause rhabdomyolysis, which causes SK muscle breakdown

P-glycoprotein transporter

• aka multi-drug resistance protein 1

• pumps toxic substances away from sensitive organs. actively expels cancer drugs from tumor cells

• ABCB1 gene variation can cause a lot of variability in drug response among patients.

pharmacodynamics

what the drug does to an organism

pharmacokinetics

what an organism does to a drug

GPCR examples

• histamine

• serotonin

• opioid

• adrenaline

• acetylcholine

• dopamine

• vision

• smell

• taste

mitogenic pathways

triggers cell division/proliferation

drugs that effect ion channels

• antiarrhythmics

• anti-epileptics

• anesthetics

what drugs target tyrosine kinase receptors

typically target mitogenic pathways

• insulin

• platelet derived growth factor

• growth hormone receptors

cyclooxygenase drugs

NSAID’s

HMG-CoA reductase drugs

target for statins

phosphodiesterases drugs

• sildinafil

• other hypertensives

• milrionone- cardiac arrest

PPAR-a nuclear receptor drugs

targets for fibrates

• gemfibrozil

glucocorticoid nuclear receptor drugs

target for cortisol and glucocorticoid steroids

estrogen nuclear receptor drugs

target for estrogen and progesterone

Aldosterone nuclear receptor drugs

target for aldosterone and spironolactone

What is drug affinity?

• how stringly a drug binds to target, quantified with assays

• affinity is the equilibrium dissasociation constant or [ ] at ½ maximal drug binding to a target

• smaller KD, higher affinity. if Drug 1 has KD 1 and Drug 2 has KD 5, drug 1 is 5 times more effective

what does a drug dose response curve tell you?

• y axis is biological response, x is log drug dose (ie Molar)

• potenency is the concentration at ½ max response. Small ED50 = potent

• efficiency is the max (desirable!) response. Higher Emax = more efficatious

• toxicity is the concentration at half of the lethal dose

• can also calculate KD and therapeutic index

how can a drug loose efficacy

• receptor desensitization: is rapid, where receptors are chemically modified to be inactivated

• receptor down regulation/ degredation: is slow (hours to days), where receptors are internalized and destroyed by proteosome. is irriversable, although new receptors can be made.

Drug agonist

activate receptors. most endogenous hormones/neurotransmitters

• full: stimulates a recepotor to 100% response. doesn’t have to bind all receptors

• partial: lower efficacy, less than 100% response even binding to all receptors

Drug antagonism

do not activate receptors, blocks agonists

• competitive: displaces agonist, reversible. Decreases potency

• non-competitive: bind to receptor, does not unbind dynamically. lasts a long time, decreases potency and efficacy

• physiological: binds to a completely different receptor and agonist and causes opposite response.

• chemical: interacts with drug to block it’s action.

Allosteric modulator

a drug that effects agonist and receptor interaction through binding to different receptor sites than the ligand. Can enhance or diminish.

• passive: enhances potency and/or efficacy of agonist.

• Negative: dimish agonist potency and/or efficacy

competative antagonist drugs

• propranolol

• naloxone

• scopolamine (anti nausea)

• dph

• spironolactone

• cimetidine (acid reflux)

non-competative antagonist drug examples

• omeprazole

• ketamine

• aspirin

• phenocybenzamine

Therapeutic index

quantifies ratio of toxicity/potency => LD50/EC50

• higher value, safer drug

• a TI of 2, means only 2 doses are fatal

theapeutic window

concentration range that a drug is effective and not harmful

combination drug effects

• additive: taking multiple drugs of the same class has an effect equal to the sum of their individual. ie antihypertensives

• synergistic effect: taking multiple drugs of the same glass produces a great effect than their sum. ie antibiotics

• idiosyncratic effect: something weird happens

narrow vs broad spectrum drugs

• narrow: targets specific bacteria species

• Broad: targets a wide range of bacteria. good when pt is critical and no time to identify bacteria

bactericidal drugs

kill invaders outright, better for life threatening infects like meningitis or immunocompromised patients

• penicillins

• cephalosporins

• flouroquinolones

• aminoglycosides

*the MBC is four or less times the MIC

bacteriostatic agents

paralize invading bacteria so host immune system can finish them.

• tetracyclines

• macrolides

• sulfonamides

Minimum inhibitory concentration (MIC)

lowest drug concentration that stops visible growth

minimum bactericidal concentration (MBC)

amount of drug needed to kill 99.9% of bacteria.

concentration vs time dependent drugs

• concentration: higher dose is better. Best to maximize peak dose above MIC 1 daily. ie aminoglycosides and fluoroquinolones

• time: long term dose above MIC is better, a higher peak has no effect. Either an infusion or frequent smaller doses. ie. penicillins and cephalosporins

Emperic vs targeted therapy

• emperic: best guest based on the likely pathogen. get the specimen sample before treatment starts.

• Targeted: a culture has been obtained and identified, use the narrowest spectrum drug possible.

Antibiotics mechanism of action

• cell wall synthesis inhibitors

• cell membrane inegrety disruptors

• protein synthesis inhibitors

• nucleic acid synthesis inhibitors

• antimetabolites

how do antivirals work

Direct Acting Antivirals (DAA) target the explication machinery, key is without harming host.

How do bacteria gain antibiotic resistance

through mutation or picking up genes for the following:

• Reduced entery: porin mutations don’t allow larger drugs inside (Gram negative)

• Drug inactivation: can gain enzymes to metabolize drugs into something harmless

• Enhanced drug efflux: multi-drug transporters will pump drugs out

• Reduced affinity to target protein: can change their receptors the drug interacts with

*mecA gene encodes an altered PBP2a to have low affinity for beta-lactrams in MRSA

Red man syndrome

can be caused by vancomycin reaction, causes flushing if drug is infused too quickly. just a histamine dump, not a true allergy

Disk diffusion test

how to tell if a antibiotic will work on a culture

• culture on agar

• soak disks in antibiotics and place on agar

• if they don’t grow, it’s a good fit- however, it is impercise and doesn’t indicate a dosage

How to calculate MBC

an agar test

• innoculate test tubes with bacteria

• use a serial dilution to introduce different drug concentrations

• when the solution is clear after incubating, all bacteria are dead or stunned

• Incubate clear solutions on agar and see if there is growth

• determine at what concentration most are dead (typically 4x MIC)

how to determine antibiotic efficiency in a clinical setting

• sample is taken

• input VIVTEC2

• will identify bacteria and possible antibiotic with success rate.

prophylactic therapy

the preventative administration after a high risk exposure. Such as surgery.

how is Beta lactamase inhibitior resistance countered?

• Resistance: enzymes in bacteria will degrade antibiotics

• so a suicide inhibitor is deployed with antibiotic, clavulanic acid, tazobectram, and sulbactram

Altering the pharmacodynamics to optimize pharmacydynamics to combat drug resistance

• prevent pt from clearing the drug too fast, bacteria are exposed for longer

• co-administer probenic that blocks the tubular secretion of penecillin, makes it much more bioavailable

antibiotic targets

• Gram positive: thick cell wall

• Gram negative: needs to fit through porins

• anaerobes: antibiotics that need O2 for transport are ineffective (several Aminoglycoside)

• atypical: live inside the host cell

Beta lactam side effects

• hypersensitivity: IgE mediated anaphylaxis to delayed maculopapular rash

• very high doses can cause neurotoxicity

• however, cross reactivity between them is low. However in the same of a penecillin allergy, monobactram is better

vancomycin limitations

• works only in gram positive, too large for gram negative

• can cause nephrotoxicity, ototoxicity, and red man

• used against sever MRSA infections. However it can gain resistance by modifying the amino acid cross link of peptide glycan terminus from D-ala-D-ala to D-ala-d-lactate

• bacteria can also create a thicker cell wall that prevents it from getting close

Cell membrane disruptors

• deptomycin binds membrane and causes ion efflux. potassium leakage arrests synthesis. gram positive

  • inactivated by lung surfactant, cannot treat pneumonia

  • clears kidneys in 8 hours

  • can cause muscle damage during prolonged use

• polymyxins target LPS and punches a hole in the cell wall. gram negative

  • kidney damage and neural side effects

both can cause collateral superinfections since it’s broad spectrum

aminoglycosides mode of action

target protein synthesis by inhibiting 30S subunit. needs oxygen to be let into cell

• causes mRNA to be misread, toxic and non-functional proteins are created. bacteriocidal

• can cause sevear, reversisible nephrotoxicity

• irreversable ototoxicity (hearing damage)

• teratogenic in pregnancy

Tetracyclines mode of action

blocks protein synthesis by targeting 30S subunits

• stops t-RNA from docking, synthesis stops. bacteriostatic.

• can cause photosensitivity

• stops calcium from being deposited in bones and tooth enamel, do not use in children 8 or younger or pregnant women

macrolides mode of action

blocks 50S subuit translocation

• azithromycin, clarithromycin, erythromycin

• Can cause GI motility stimulation (diarrhea), cholestatic hepatitus

• aside from azithromycin, potent CYP450 (liver enzymes that metabolizes chemicals) inhibitors

Chlorapheninol mode of action

blocks 50S peptide bond formation

• high doses can cause bone marrow supression

• can cause gray baby syndrome in infants due to an inhibited liver enzyme for the formation of glycogen

clindamycin mode of action

blocks 50S peptide translocation

• best for anerobic infections located above diaphragm, such as pneumonia

• anerobic infections in diaphram

How to remember protein synthesis inhibitors

buy AT 30, CELL at 50

• Aminoglycosides, tetracyclines => 30S

• Chloramphenicol, Clindamycin, erythromycin (macrolides), linezolid =>50S

floroquinones

inhibits topo II in Gram negative bacteria, DNA supercoils. inhibits Topo IV in gram positive, prevents separation of replicated chromosomes

• Ciprofloaxin and levofloxacin

• can cause Achilles tendon rupture and cartilage damange

• not for pregnant women or growing children

Rifamycins

binds to beta DNA dependent RNA Pol, halts RNA transcription

• known for TB multi-drug therapy and prophylaxis for neisseria meningitis contacts

• most potent inducer of CYP450 enzyme, rapidly clears out other drugs coadministered.

• harmless red/orange discoloring of body fluids

Folic Acid Antimatabolites

sulfanomides (blocks dihydropterotate synthase) are administered with trimethoprin (blocks dihydrofolate reductase). Without folate, DNA/RNA/proteins cannot be made

• can cause sever hypersensitivity reactions, such as toxic epidermal necrolysis.

• is an oxidizing drug, not for PT with G6PD deficency

• high doses causes bone marrow suppresion

• high potassium ion concentration in blood

*Bactrim is the best drug for primary prophylaxis/treatment for pneumocysticpneumona in immunocompromised pt

how many fungi species are pathogenic?

roughly 300, severity usually depends on pt comorbidities

What is targeted for fungi?

• outer cell wall- chitin

• membrane- ergosterol

echinocandins

a type of antifungal that breaches the cell wall

• block beta glucan synthase to progressively weaken cell wall

• caspofungin

• not good blood-brain barrier penetrator

• fungicidal

polyenes

pore the membrane

• amphyotericin B and Nystatin binds to ergosterol to create leaky pores

• fungicidal

pyrimidine antifungals

inhibits RNA/DNA synthesis

• flucytosine

• fungistatic

antifungal collateral damage

• Amphotericin B: nephrotocicity

• Flucytosine: Bone marrow suppression and superinfection by wiping out gut flora

• Azoles: hepatotoxicity by stopping metabolic processing

target for antivirals

the steps of a viral life cycle, specific enzymes used

Class 1 antivirals: anti-herpatic drugs

pro-drugs must be phosphorylated by viral thymidine kinase in cell to be active

• acyclovir: guanosine analog, is a chain terminator in viral replication by targeting viral DNA polymerase.

• Can form crystals in kidney, so heavy hydration is best.

• valacyclovir: converts to acyclovir in body for better absorbtion

Class 2: antinfluenza drugs

RNA virus, targets the cleaving of the tether (neuraminidase) at the membrane after the new viruses start to envelope. By inhibiting it, viruses cannot be released. must be administered within 48 hours of symptom onset

• olsatamivir (pill)

• zanamivir (inhaled), can cause bronchospasm

Class 3 antivirals: HIV reverse transcriptase inhibitors

competitively inhibits reverse transcriptase, viral RNA cannot be turned into DNA. nucleotide chain terminates the enzyme early.

• zidovudine- need phosphylization by host enzymes along with most of these drugs

• tenofovir- does not have to be phosphorylated to work

• can cause lactic acidosis, and bone marrow supression

cartilage function

a type of avascular connective tissue

• structural support while maintaining flexability

• low friction surface

• resisits compression

• slow healing and repair (because it’s avascular)

• different types are classified based on extracellular matrix

hyalin cartilage characteristics

• most abundant

• hydrated ECM (translucent in microgram), rich in type 2 collagen

• surrounded in perichondrium

• in bone, tendons, ligaments, ribs, nose, trachea/bronchi

• fetal skeleton

hyaline cartilage functions

• smooth and low friction surface

• template for endochondral bone formation

elastic cartilage charateristics

• rich in type 2 collagen and abundant elastic fibers (visable in micrograph)

• surrounded by perichondrium

• avascular

• external ear, epiglottis, eustation tube

elastic fiber function

maintains shape even after repeated bending

fibrocartilage characteristics

• abundant in type 1 cartilage

• thick collagen bundles in rows, chondrocytes in between on lines of stress

• no pericondrium, so only interstitial growth

• tendons/ligaments (some), IV discks, menisci of knee

fibrocartilage functions

• more similar to bone- high strength and compression resistance

• shock absorber

mesenchymal cells

cartilage precursor, also creates adipocyte, myocytes, and osteoblasts. are differentiated by bone morphogenics proteins.

bone morphogenic proteins

• growth factors that stimulate bone and cartilage msc differentiation

• ex. transforming growth factor, really any bone/certilage growth factor

BMP receptors

• types 1 and types 2. Type 2 activates type 1 to trigger response

• extracellular

• intracellular response- recruits receptor smad proteins and phosphorylated by type 1

• 2 r-smads form complex with smad4

• smad complex translocate to nucleus to regulate transcruiption

• upregulates sox9 (chondroblasts) and runx2 (osteoblasts) gene

Sox9

key transcription factor for chondroblast differentiation

• upregulates sox-5 and sox-6. trio will induce cartilage specific genes

osteochondro-progenitor cell

expression of both sox-9 and runx2

• sox9/5/6 will trigger chondroblasts

• runx2 and beta catenin will trigger osteoblasts

where are mesncymal stem cells found in cartilage

in the perichondrium- outside of tissue

• first turns into chondroblast: a immature cartilage cell. eliptical shape, found near perichondrium

• chondrocytes: mature cartilage cells, rounder in shape, deeper in tissue. are found in lacunae, or a pocket in the extracellular matrix.

  • expand tissue through mitotic division, forms isogenous groups. maintain ECM

apositional growth

growth on the surface, what bone and cartilage cells go through. only tissue example in humans

bone special characteristics

• very vascular

• continuously remolded

• capable of repair after injury

2 main types of bone

• compact (cortical bone)- dense outer layer, for strength

• spongy (trabecular)- tunnel network (trabeculae) filled with bone marrow. reduces overall weight of bone