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Pharmacology Test 4 > Theory > Flashcards

Theory Flashcards

1
Q

name the 4 processes of pharmacokinetics

A
  • absorption
  • distribution
  • metabolism
  • excretion
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2
Q

passage of drugs across membranes

A
  • membranes are close, so drugs must often pass thru cells not between
    • the barrier is the cytoplasmic membrane
  • 3 ways to cross:
    • channels and pores: only allows small ions thru like Na and K
    • transport systems: can be active or passive
      • all are selective
    • direct penetration of membrane: which requires a drug be lipid soluble
      • polar mcs and ions are not lipid soluble, so can’t penetrate, so they would have to be carried across with a protein b/w cells
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3
Q

P-glycoprotein

A
  • multi-drug transporter protein
    • transports many drugs out of cell
    • found in liver, kidney, placenta, intestine, capillaries, brain
      • helps get drugs eliminated, away from fetus, or out of the brain
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4
Q

explain ion trapping/pH partitioning

A
  • pH differs on each side of membrane, so mcs accumulate where pH favors ionization
    • acidic drugs accumulate on basic side of the membrane
    • basic drugs accumulate on acidic side of the membrane
  • absorption is enhanced when difference b/w pH of the blood and that of the site of administration is such that a drug will be ionized in the blood
    • acidic drugs ionize in basic media, so they will accumulate on the basic side, so if blood is more basic than site of administration, then absorption occurs
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5
Q

what are the 5 factors affecting absorption?

A
  • rate of dissolution
    • dissolve before can be absorbed
  • surface area: large SA, higher absorption rate
    • orally administrated drugs often absorbed from small intestine b/c of the microvilli, so the SA is larger
  • blood flow: high blood flow, high absorption rate
    • maintains gradient that is higher b/w drug outside the blood and drug inside the blood
  • lipid solubility: if lipid soluble, they can directly cross the membrane
  • pH partitioning/ion trapping
    • absorption inc when difference b/w pH of blood and pH at the site of administation is such that drug mcs will have tendency to become ionized in the blood
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6
Q

what are the 2 groups of routes that drugs may be administered?

A
  • enteral: via GI, oral (PO)
  • parenteral: intravenous (IV), subcutaneous, intramuscular (IM)
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7
Q

movement of drugs following GI absorption

A
  • starts in GI tract and gets absorbed thru the wall of the GI tract into the blood
  • then first goes to the portal V–>liver where it either
    • is made to be more polar, more water soluble
    • is glucuronidated: so a glucose derivative is added to the lipid soluble drug
  • then the drug can either go:
    • out to the IVC–>heart–>general circulation–>eventually excreted in the kidney
    • (for glucuronidated drugs) go out into bile–>back into the GI tract where it is broken back down into the drug and the glucose–>can either be:
      • excreted in the feces
      • be reabsorbed further down the GI tract into the blood–>portal vein–>liver
  • this is a cycle called entero hepatic cycling
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8
Q

3 factors affecting distribution

A
  • blood flow to tissues: rate at which blood flows determines rate at which drug is delivered to target organ
  • exiting vascular system via capillary beds
    • in capillaries, drugs can pass b/w and not thru cells so no resistance
    • BBB: tight junctions b/w cells which prevent drug passage
      • only lipid soluble drugs or those with transport systems can cross
      • P glycoprotein protects CNS
    • placental drug transfer
    • protein binding to plasma albumin
  • entering cells: determined by lipid solubility and transport systems
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9
Q

explain how placental drug transfer affects distribution

A
  • lipid soluble and non-ionized drugs can pass across placenta to fetus
  • ionized, highly polar, protein bound, or substrates of P glycoprotein cannot get to fetus
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10
Q

explain how protein binding to plasma albumin can affect drug distribution

A
  • drugs can reversibly bind to protein
    • plasma albumin: always in bloodstream b/c so large
      • drugs bound to albumin can’t leave blood, only free mcs can leave blood
    • can be a source of drug interaction b/c drugs competing for sites on albumin
      • if displace a drug, the free conc of the displaced drug can inc, so that drug’s response is increased
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11
Q

metabolism of drugs

A
  • mostly done in the liver
    • done by the P-450 enzyme system
  • irreversible transformation of parent cpds into daughter cpds then disbursed thru the body
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12
Q

metabolism and age

A
  • infants have limited ability to metabolize
    • drugs are not tested on very young b/c their kidneys and liver and immature
  • older adults have a decreased ability
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13
Q

drug metabolizing enzymes

A
  • some drugs metabolized by P-450 b/c they are substrates of P-450 enzyme system
  • inducers: act on liver to increase rate of drug metabolism
    • as metabolism inc, drug plasma levels decrease, and kidney function inc (so creatinine decreases)
    • 2 consequences:
      • if also substrate, can mandate inc dosage to maintain effects
      • can accelerate metabolism of other drugs and mandate an increase in their dosage
  • inhibitors: decrease rate of metabolism of drugs
    • as drug metabolism dec, blood plasma rates increase, and kidney function dec (so creatinine levels inc)
      • can cause inc toxicity and bad S/E
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14
Q

explain the first pass effect

A
  • rapid hepatic inactivation of certain oral drugs
    • sometimes, drug b/c goes from GI–>portal V–>liver can be inactivated when first going thru liver, so have to be administered parenterally
    • if liver capacity to metabolize drug is high, then it can ianctivate the drug on the first pass thru the liver
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15
Q

drug metabolism and nutrition

A
  • P450 enzymes require co-factors to function
  • if malnourished, then not getting enough protein to maintain muscle mass, and water is stored in muscle
    • if wasting of muscle occurs, then drugs that are water soluble have too much drug in blood stream following subsequent doses so can become toxic
    • especially occurs in the elderly
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16
Q

competition b/c drugs and their metabolism

A
  • if 2 drugs metabolized by the same pathway, can decrease rate at which one is metabolized and may build up
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17
Q

steps in renal excretion of drugs

A
  • glomerular filtration
    • blood w/ drugs comes in capillaries where forced thru pores, but blood cells and bound drugs stay behind in the capillaries b/c too large
  • passive tubular reabsorption
    • lower concentration of drug in blood than urine drives lipid soluble drugs back to blood, so have to convert lipid soluble drugs to more polar form to excrete, so that it will stay in the urine
    • if not lipid soluble, then continues on in urine
  • active tubular secretion
    • pump drugs from blood to kidney lumen
      • one pump for each organic acids, organic bases, and P glycoprotein
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18
Q

factors that modify renal excretion of drugs

A
  • pH dependent ionization
    • by manipulating urine pH to promote ionization of the drug, you can dec passive reabsorption of drug back to the blood
      • so if we have an acidic drug and make the urine basic, the drug will more likely be ionized, so it will not be carried back to the blood by passive tubular reabsorption
  • competition for active tubular transport can delay renal excretion and prolong drug effects
    • can only carry so much at once, so if drug doesn’t go back to urine, then effects are pro-longed
  • age
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19
Q

routes of non-renal excretion

A
  • breast milk: lipid soluble drugs can be passes to infant in breast milk
  • bile: excreted to small intestine–>feces
  • lungs: excrete volatile anesthetics
  • sweat and saliva
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20
Q

Grapefruit Juice and Cytochrome P-450

A
  • Grapefruit juice: many medications interact with grapefruit juice
    • More a pt drinks, the more inhibition of CYP3A4 that occurs
    • Dec first pass metabolism of drugs, so inc the bioavailabilty of the drug
  • CYP3A4 is found both in the liver and the intestinal wall
    • with grapefruit juice, that on the intestinal wall is inhibited more, which decreases the intestinal metabolism of many drugs, so the amount available for absorption inc–>inc levels of the drug in the blood–>more intense drug effects
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21
Q

what changes to the body does pregnancy bring about as it relates to pharmacokinetics?

A
  • Pregnancy brings about changes in the kidney, liver, GI tract, so change in dosage may need to occur
    • 3rd trimester, the renal blood flow is doubled, so inc in glomerular filtration rate, so the drugs eliminated by glomerular filtration experience inc clearance
    • Hepatic metabolism inc
    • GI motility and tone decrease, so there is prolonged time for drugs to be absorbed or reabsorbed in enterohepatic circulation
      • Inc levels of drugs whose absorption is usually poor
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22
Q

what does the effect of a teratogen depend on?

A
  • dependent on which stage of pregnancy drug is given
    • preimplantation (conception-week 2)
      • if dose of drug is high, death will occur to baby
    • embryonic (weeks 3-8)
      • exposure to teratogens causes gross malformation
    • fetal (weeks 9-term)
      • teratogen exposure disrupts function rather than structure
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23
Q

why are pediatric pts sensitive to drugs?

A

organ system immaturity

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24
Q

what kind of effects do you see with drugs in neonates?

A
  • drugs have intense and prolonged effects
    • levels remain above MEC longer than in adult, so effects are prolonged
    • with a subQ injection, levels remain above MEC longer and levels rise higher, so effects more intense and prolonged
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25
Q

why do we have inc drug sensitivity in pediatric pts?

A
  • immaturity of 5 processes:
    • drug reabsorption
    • protein binding
    • exclusion of drugs from CNS by BBB
    • hepatic drug metabolism
    • renal drug excretion
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26
Q

absorption orally for pts under 1 yo

A
  • if drug absorbed in stomach, then longer gastric emptying time, so inc absorption
  • if drug absorbed in intestine, then delay in effects of drugs b/c of longer gastric emptying times
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27
Q

absorption intramuscularly for pt under 1 yo

A
  • absorption is slow and erratic
    • slow b/c low blood flow to muscles
    • but, by early infancy, absorption is more rapid than in adults
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28
Q

absorption transdermally for pts under 1 yo

A
  • more rapid and complete
    • stratum corneum is thin and blood flow to skin is higher
    • inc risk of toxicity from topical drugs
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29
Q

distribution in pts under 1 yo

A
  • protein binding
    • limited b/c of low levels of albumin and endogenous cpds compete with drugs for the limited amt of binding sites
      • so more free medication in infants, which intensifies results, so dosages should be reduced
  • BBB
    • not fully developed so drugs have easy access to CNS
      • so give in smaller doses
30
Q

hepatic metabolism in pts under 1 yo

A
  • metabolism is low in newborns
    • sensitive to drugs that are eliminated by hepatic metabolism
    • adult levels reached by age 1
31
Q

renal excretion in pts under 1 yo

A
  • reduced at birth
    • renal blood flow, glomerular filtration, and tubular secretion are all low
    • if drug eliminated by renal excretion then need reduced dose or at longer intervals
  • adult levels reached by 1 yo
32
Q

PK for children 1 YO and older

A
  • similar to adults
  • BUT metabolize drugs faster than adults until 6 yo
    • so may need inc in dosage or reduction in dosing intervals for drugs eliminated by hepatic metabolism
33
Q

why do geriatric pts have more adverse rxns and more drug drug rxns?

A
  • altered pharmacokinetics secondary to organ system degeneration
  • multiple and severe illnesses
  • multi drug therapy
    • polypharmacy
  • poor adherence
34
Q

changes in absorption in geriatric pts

A
  • GI absorption:
    • percent of oral dose that becomes absorbed does not change
    • rate of absorption may be slowed b/c of delayed gastric emptying so drug responses may be delayed
35
Q

changes in distribution in geriatric pts

A
  • inc body fat: provides storage for lipid soluble drugs so plasma levels of these are reduced and there is less of a response
  • dec lean body mass and total body water
    • water soluble drugs become distributed in smaller volume, so the concentration is inc and the effects may be more intense
  • reduced conc of albumin
    • inc levels of free drug so effects may be more intense
36
Q

changes in metabolism in geriatric pts

A
  • rates of hepatic metabolism decline due to:
    • reduced hepatic blood flow
    • reduced liver mass
    • dec activity of liver enzymes
      • all lead to prolonged exposure of certain drugs
  • Depending on the way drug is metabolized during first pass effect, there is usually a first phase and a second phase, but they lose the first phase, so only have second phase which include glucuronidation, acetylation, and sulfuration (all old folks have GAS), so many times drugs that need a lot of metabolism should not be given to the elderly
37
Q

changes in excretion in geriatric pts

A
  • renal fcn declines
    • drug accumulation secondary to reduced renal excretion is most important cause of severe adverse rxns in older adults
    • all due to reduced renal blood flow, glomerular filtration rate, tubular secretion, and number of nephrons
  • should check creatinine clearance
38
Q

why would parenteral injections be preferred to oral preparations?

A
  • emergencies if need rapid medication onset
  • situtations where plasma drug levels need to be tightly controlled
  • drugs that would be destroyed by gastric acid, GI enzymes, or hepatic enzymes
39
Q

parenteral routes: speed of absorption

A
  • IV>IM>subQ
    • subQ slowest b/c relies on capillaries to distribute
40
Q

gender differences in drug responses

A
  • do not know how a lot of medications will react in women b/c more studies conducted on men
  • Pregnant pt:
    • A: okay to give
    • X: don’t give b/c high risk
  • Can affect sperm quality or quantity for men
41
Q

explain an agonist

A
  • drug binds to its receptor and mimics actions of body’s own regulatory compounds
    • drug that is an agonist works in the same way as a desired chemical in the body
    • have affinity and high intrinsic activity
42
Q

explain an antagonist

A
  • block the agonists (whether endogenous or exogenous) from stimulating the receptors
    • prevents normal rxn from occurring
    • has affinity for receptor by no intrinsic activity, so prevents R activation and normal processes from occurring
  • act by preventing receptor activation
    • so, if no agonist is present, administration has no observable effect
43
Q

what happens if the receptors of a cell are continually exposed to an agonist?

A
  • cell becomes less responsive
    • it is said to be “desensitized”
    • could occur by down regulation meaning the cell actually breaks down some of the receptors that normally responded to the agonist
44
Q

what happens if the receptors of a cell are continually exposed to an antagonist?

A
  • the cell becomes hypersensitized
    • up regulation occurs by more receptors being created to respond to the antagonist
45
Q

explain an allergic rxn

A
  • it is an immune response caused by an Ag
  • will present as anaphylaxis: bronchospasm, laryngeal edema, hypotension
    • need to use epinephrine which will cause:
      • bronchodilation
      • vasoconstriction to return BP to normal
        • works by activating beta 1 receptors in the heart and beta 2 in the lungs
46
Q

which drugs cause most allergic rxns?

A
  • penicillins: most common
  • NSAIDs
  • sulfonamides: diuretics, antibiotics
47
Q

explain therapeutic range

A
  • when drug levels are high enough to be effective (so above MEC), but not high enough to be toxic
    • so falls b/w MEC and toxic concentration
    • it is the range where the drug concentration will cause therapeutic effects in the majority of patients, and adverse rxns in the minority of patients
  • narrow therapeutic range is more dangerous and harder to dose safely, b/c very narrow range from MEC to toxic level
48
Q

what is the minimum effective concentration?

A
  • lowest possible level in which a drug would give any therapeutic effects
49
Q

when are peak and trough levels in drug serum concentration?

A
  • peak level is 30 minutes after a drug is given
  • trough level is 30 minutes before the next dose of a drug is given
50
Q

what is the loading dose?

A
  • higher dose is used to increase drug levels in the body quickly
    • once give, the drug level will be closer to the therapeutic dose and a normal dose can be given
51
Q

what determines the duration of action of a drug?

A
  • metabolism
  • excretion
52
Q

what makes a drug dangerous and harder to dose safely?

A
  • a narrow therapeutic range, so small range b/w MEC and toxic dose level
53
Q

explain half life

A
  • how rapidly amount of drug declines in the body by half based on metabolism and excretion
    • time for amount of drug in body to decrease by 50%
  • determines the dosing interval
    • so the shorter the half life of the drug, the shorter the dosing interval to maintain therapeutic effects
54
Q

explain the process of repeated dosing to reach a plateau

A
  • Drug accumulates in body until it reaches plateau (steady level)
    • Amt of drug eliminated b/w doses equals the dose administered
      • Average drug levels will remain constant and plateau
      • Typically takes 4 half lives
      • Not dependent on dosage size
55
Q

epi-pen considerations

A
  • Epinephrine: adrenergic drug
    • Inc Cardiac outpuut–>elevates BP
    • Suppresses glottal edema
    • Counteracts bronchoconstriction
    • Single use, spring activated needle, IM injection in outer thigh (can give thru clothing) for 10 sec, massage for 10 sec following injection
    • After use: call 911, go to ER
      • Effects start to fade in 10-20 min
      • Enzymes broken down so drug will metabolize quickly
      • After calling 911, you need to administer a second dose if the symptoms don’t go away
      • Then after you give epi, you need to give just a regular steroid to continue to decrease allergic symptoms
  • Can be used with lidocaine/novocaine b/c it causes it to work longer
56
Q

drug selectivity

A
  • selectivity of a drug is possible b/c they act on specific receptors
    • you want the drug to be selective, so it will cause fewer side effects
    • if drug selective for a receptor that regulates a few processes, drug that works on that receptor will also have effects on all of the processes even if not intended use
57
Q

what does potentiating mean?

A
  • when a patient is taking 2 medications, one drug may intensify or potentiate the effects of the other
    • this is a potentiative interaction
  • these types of interactions can be:
    • beneficial: can cause increased therapeutic effects
    • detrimental: can cause an increased risk for adverse effects (ie. aspirin and warfarin)
58
Q

what is synergy?

A
  • When the interaction causes an increase in the effects of one or both of the drugs the interaction is called a synergistic effect.
59
Q

what does 1 oz equal?

A

=2 tbsp=6 tsp=30 mL

60
Q

define pharmacokinetics

A
  • what the body does to drug
61
Q

define pharmacodynamics

A
  • what the drug does to the body
62
Q

which medication PO is the fastest absorbed?

A

liquid medication

63
Q

which populations are at the highest risk for ADRs?

A

very young and the very old

64
Q

what are the types of allergic rxns and how do you treat each?

A
  • mild rash: contact dermatitis
    • _​_tx: diphenhydramine
  • rash that is more broadly spread over the body
    • tx: larger dose of diphenhydramine or a steroid
  • hives and difficulty breathing: anaphylaxis
    • _​_tx: epinephrine
65
Q

if the pt’s liver is impaired, what happens with water soluble drugs?

A
  • they stay in the body longer, so their effects last longer
    • if another dose is given, this could lead to build and possible toxicity
66
Q

Who would we want to be careful of recommending NSAIDS to?

A

those with renal problems

67
Q

what is first peak effect?

A
  • especially for HTN, you want to watch these, b/c the first one can cause you to have hypotension
  • So with first meds, you need to monitor the first dose
68
Q

7 Rights of Med Administration

A
  • right patient
  • right medication
  • right route
  • right dose
  • right time
  • right indication
  • right documentation
69
Q

how long will grapefruit juice stay in your system?

A

2 days or more

70
Q

what is therapeutic objective?

A

to provide maximum benefit with minimal harm

Pharmacology Test 4 (10 decks)

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