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APEX > Pharmacology I > Flashcards

Pharmacology I Flashcards

1
Q

Define volume of distribution and recite the equation

A

Vd = administered drug/desired concentration

-Vd describes the relationship between a drug’s plasma concentration following a specific dose. A theoretical measure of how a drug distributes throughout the body.

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2
Q

What are the implications when a drug’s Vd exceeds TBW?

A

> 42 L
0.6 L/kg

The drug is lipophilic. And it requires a higher dose to achieve a given plasma concentration. I.e., propofol, fentanyl

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3
Q

What are the implications when a drug’s Vd is less than TBW?

A

< 42 L
< 0.6 L/kg

The drug is hydrophilic. Rocuronium, albumin.

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4
Q

How do you calculate a loading dose for an IV medication?

A

= Vd x (desired concentration/bioavailability)

-an IV drug always has a bioavailability of 1.

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5
Q

What is clearance? What increases or decreases it?

A

Increased by: increased blood flow, increased drug dose, increased extraction ratio

Decreased by: half life and drug concentration in central compartment

Clearance = the volume of plasma that is cleared of a drug per unit time.

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6
Q

How many 1/2 times for a steady state to be achieved?

A

5

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7
Q

what is the alpha vs beta distribution phases on the plasma concentration graph

A

alpha - distribution (from plasma to the tissues)
beta - elimination (begins as plasma concentration falls below tissue concentration). the concentration gradient reverses, which causes the drug to re-enter the plasma

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8
Q

context sensitive half time of opioids

A

fentanyl > alfentanil > sufentanil > remifentanil

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9
Q

what is the difference between a strong and weak acid?

A

the degree of ionization. if you put a strong acid or a strong base in water, they will completely ionize.

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10
Q

what is ionization? what 2 factors determine how much a molecule will ionize?

A

the process where a molecule gains a positive or negative charge. its dependent on pka of the drug and pH of the solution

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11
Q

non-ionized

A

= lipophilic, will be hepatically biotransformed

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12
Q

what happens if you put an acid in a basic solution

A

weak acids will be more ionized and water soluble

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13
Q

how can you tell if a drug is an acid or base based on its name?

A

DRUGS ARE PREPARED AS A SALT THAT DISSOCIATES IN A SOLUTION

weak acid is paired with a positive ion (sodium, calcium, magnesium)
-sodium thiopental

weak base is paired with negative ion (chloride, sulfate)
-morphine sulfate, lidocaine hydrochloride

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14
Q

name 3 key plasma proteins

A

albumin (acidic drugs)
alpha 1 acid glycoprotein (basic drugs)
beta globulin (basic drugs)

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15
Q

what reduces albumin concentration?

A

age
pregnancy
malnutrition
renal/liver dx

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16
Q

what decreases a1acid

A

pregnancy
neonates

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17
Q

what increases a1acid

A

elderly
chronic pain, RA
surgery, MI

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18
Q

how do you calculate changes in plasma protein binding?

A

new - old / old

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19
Q

a new anesthetic drug is cleared from the body at a rate proportional to its plasma concentration. what kind of kinetic order describes this?

A

first order

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20
Q

When there is more drug than enzymes….

A

zero order
aka: ETOH, phenytoin, ASA, theophylline, warfarin, heparin

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21
Q

what is the function of a phase 1 reaction? list three examples

A

MODIFICATION (lipophilic > hydrophilic)

hydrolysis (typically a water molecule breaks an ester bond)
reduction (add an electron)
oxidation (remove an electron)

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22
Q

what is the function of phase 2 reaction?

A

conjugation

-glucuronic acid, glycine, acetic acid, sulfuric acid, methyl group

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23
Q

discuss enterohepatic circulation and give 2 examples

A

conjugated compounds excreted into bile > reactivated in intestine > reabsorbed into systemic circulation

diazepam & warfarin

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24
Q

what is the extraction ratio?

A

how much drug is delivered to a clearing organ vs how much drug is removed

arterial concentration - venous concentration / arterial concentration

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25
Q

what is perfusion-dependent elimination

A

ER > 0.7, dependent on Q

-fent/sufent/morphine/meperidine
-naloxone
-ketamine/prop/lido
-bupi
-metoprolol, propanolol
-nifedipine, diltiazem, verapamil

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26
Q

what is capacity-dependent elimination

A

ER < 0.3, dependent on enzymes or protein binding

-rocuronium, diazepam, lorazepam, methadone, thiopental, theophylline, phenytoin

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27
Q

Name hepatic inducers (6)

A

tobacco, ETOH
barbs
phenytoin
rifampin
caarbamazepine

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28
Q

Name hepatic inhibitors (7)

A

grapefruit juice
SSRIs
cimetidine
omeprazole
erythromycin
ketoconazole
isoniazid

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29
Q

What drugs are metabolized by nonspecific esterases?

A

esmolol
clevidipine
remifentanil
remimidazolam
atracurium
etomidate (+hepatic)

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30
Q

what drugs are metabolized by pseudocholinesterases?

A

succinylcholine
mivacurium
ester LA (cocaine + liver)

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31
Q

What is Lusedra?

A

fospropofol (prodrug)

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32
Q

what is pharmacobiophysics?

A

considers the drug’s concentration in the plasma and the effect site (biophase)

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33
Q

what does a steep sleep on the dose-response curve tell you?

A

small increase in dose can have a profound clinical effect.

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34
Q

therapeutic index

A

TD50/ED50

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35
Q

what is chirality?

A

one carbon with tetrahedral bonding (bonds with 4 different atoms)

1 chiral carbon = 2 enantiomers

36
Q

what is an enantiomer?

A

chiral molecules that are non-superimposable mirror images

37
Q

what are the cv and respiratory effects of midaz?

A

cv = at sedation doses, nothing. at induction doses … drops the SVR and BP

respiratory= sedation doses, shifts co2 response curve to the right (esp. with fentanyl).

pt with copd are more senstiive to the respiratory depressant doses

38
Q

cns effects of midazolam

A

induction dose = drops cmro2 and cbf.

cannot produce an isoelectric EEG (barbs and propofol can)

anticonvulsant, anxiolysis, antispasmotic

39
Q

what are the unique features of remimazolam?

A

vial protected from light and discard 8 hours

metabolized by plasma esterases

c/i with patients with a hypersensitivity to dextran

40
Q

how long does flumazenil last

A

30 - 60 mins
0.2 mg, 0.1 mg q1m

41
Q

how many flourine ions are in each volatile agent

A

iso = 5 Fl
des = 6 Fl
sevo = 7 Fl

halothane - 3 flourine and one bromine

42
Q

which volatile agents are most identicle

A

iso and des.
des has a flourine atom instead of a chlorine

43
Q

what does full fluorination do

A

decreases potency
increases vapor pressure
decreases hepatic biotransformation

44
Q

why is sevo more potent than des

A

BULKY PROPYL SIDE CHAIN

45
Q

what is vapor pressure and how is it affected by ambient temperature?

A

the pressure exerted by a vapor when it is in equilibrium with its liquid or solid phase.

increase temperature increases vapor pressure

46
Q

how is anesthetic delivery affected by altitude? when does this matter?

A

vol % x ambient pressure

so if you are at high altitude, you can underdose des b/c it does not have a temperature compensating valve like sevo and iso

47
Q

vapor pressure of sevo, des, iso, n2o

A

sevo - 157 mmHg
des - 669 mmHg
iso - 238 mmHg
n2o - 38,770 mmHg

48
Q

which inhalational anesthetics are stable in soda lime? whaat byproducts can each agent produce in soda lime?

A

sevo - not stable, compound A (happens in function and dried soda lime)

des- not stable (CO)
iso - not stable (CO)
N2O - stable (none!!)

49
Q

what is solubility? how do we measure it?

A

the tendency of a solute to dissolve into a solvent. aka the agent’s ability to dissolve in the blood and tissues.

blood:gas solubility

how much of the gas is in the blood vs alveoli.

___ part per blood vs. 1 part per alveoli

50
Q

b/g solubility for sevo, des, iso, n2o

A

sevo = 0.65
des = 0.42
iso = 1.4
n2o = 0.46

51
Q

how do we establish an anesthetic concentration inside the alveolus?

A

-vaporizer on = Fi
-ventilation washes anesthetic agent into alveoli = FA
-buildup of anesthetic partial pressure inside the alveoli is opposed by the continuous uptake of the anesthetic into to the blood. = uptake
-CO distributes it throughout the body = distribution

52
Q

what increases the rate of FA/FI via delivery

A

-increased vaporizer setting (increased FGF)
-decreased time constant of the delivery system
-decreased anatomic dead space
-increased alveolar ventilation
-decreased FRC

53
Q

what increases the uptake

A

-low blood gas solubility
-low CO
-low partial pressure gradient between the alveolar gas and mixed venous

54
Q

what are the four tissue groups?

A

-VRG - heart, brain, kidneys, liver, endocrine glands = 10%, receives 75% of CO
-Muscle - skeletal muscle, skin 50%, receives 20% of CO
-Fat = 20%, receives 5% of CO
-VPG = 20%, receives < 1% of CO. bones, tendons, cartilage

55
Q

how are inhalational anesthetics removed form the body?

A
  1. alveoli (ventilation)
  2. hepatic biotransformation
  3. percutaneous loss (minimal)
56
Q

discuss the hepatic biotransformation of the inhaled anesthetics

A
  1. n2o = 0.004
  2. des = 0.02
  3. iso = 0.2
  4. sevo = 2
  5. halothane = 20
57
Q

what is 1 mac hour

A

sevo at 2% for 1 hour
sevo at 1% for 2 hours

58
Q

which volatile agents are metabolized to trifluouracetic acid?

A

halothane
isoflurane
desflurane

potential consequence = immune mediated hepatic dysfunction (especially in a patient with previous TFA exposure)

59
Q

theoretical consequences of sevoflurane metabolism

A

liberation of flouride ions d/t high degree of metabolism

-high output renal failure
-polyuria, hypernatremia, hyperosmolarity, increased plasma creatinine, inability to concentrate the urine

60
Q

what is the concentration effect

A

increased alveolar uptake as the concentration of a gas is increased. d/t two mechanisms.

  1. concentraTING effect: n2O volume going from alveolus to pulmonary blood is much higher than the amount of nitrogen moving in the opposite direction. this causes the alveolus to shrink. the reduction in alveolar volume = relative increase in FA.
  2. augmented gas inflow: on the subsequent breath, the concentrating effect causes an increased inflow of tracheal gas containing the anesthetic agent to replace the lost alveolar volume. this increases alveolar ventilation and augments FA. (temporary)
61
Q

why does FA/FI rise faster for n2o than des

A

concentration effect.

alveolar partial presssure of N2O rises faster than desflurane. this is because we can safely deliver a higher inspiratory concentration which negates the small difference imposed by the slightly higher b/g coefficient

62
Q

anesthetic overpressure results in a more profound effect for which agents

A

higher blood solubility

63
Q

which IA are most greatly affected by a right to left shunt

A

low b/g solubility
DESFLURANE

64
Q

why does n2o accumulate in closed air space?

A

34x more soluble than nitrogen.

n2o = 0.46
nitrogen = 0.014

65
Q

where does n2o increase pressure

A

pulmonary blebs, air bubble sin blood, gas bubbles in eye (fast equilibration)

slow equilibration = bowel, pneumoperitoneum

fixed airspaces - middle ear, brain

66
Q

how does nitrous affect a patient with an ocular gas bubble?

A

S56 bubble
-d/c nitrous oxide 15 mins prior to placement of bubble. post placement, do not use nitrous for 7 - 10 days

air bubble
-do not use nitrous for 5 days

silicone bubble
-ok to use nitrous

perfluoropropane
-do not use nitrous for 30 days

67
Q

what is the mac for nitrous

A

104

68
Q

what is mac bar

A

1.5

MAC required to block autonomic response after a supramaximal pain stimulus

69
Q

what is mac awake

A

during induction = 0.3 - 0.4 MAC

emergence = 0.15 MAC

this is the MAC when a patient willl open their eyes

70
Q

what factors increase MAC

A

-hypernatremia
-MAOIs, ephedrine, amphetamines, acute cocaine, levodopa
-chronic ETOH
-red head (19%)
-infant 1 - 6 mo (sevo is the same for neonates and infants)
-hyperthermia

71
Q

what factors decrease MAC

A

-hyponatremia
-acute ETOH
-lithium, lidocaine, hydroxyzine, opioids (etc.)
-hypothermia
-preemies and elderly (6% decrease per decade post 40)
-hypotension (MAP < 50)
-hypoxia, anemia (<4.3 mL O2/dL)
-CPB
-metabolic acidosis
-hypoosmolarity
-pregnancy —> PP 24 - 72 hours
-PACO2 > 95

72
Q

what factors do not affect MAC?

A

potassium
magensium
thyroid problems
gender
PaCO2 15 - 95 mmHg
HTN

73
Q

what is meyer-overton rule?

A

lipid solubility is directly proportional to the potency of an inhaled anesthetic.

-the number of anesthetic molecules that are dissolved in the brain determine the depth of anesthesia

74
Q

what is the unitary hypothesis?

A

all anesthetics share a similar MOA although each at a different site

75
Q

most important site of halogenated anesthetic action?

A

GABAa
increases the duration it is open

76
Q

what cerebral receptors are stimulated by nitrous oxide

A

nmda antagonism
potassium 2p-channel stimulation

NO GABA

77
Q

where do halogenated agents produce unconsciousness

A

thalamus
cerebral cortex
reticular activating system

78
Q

where do halogenated agents produce amnesia

A

amygdala
hippocampus

79
Q

how do halogenated agents decrease blood pressure

A

decrease intracellular calcium in VSM = vasodilation = decreased venous return

decrease intracellular calcium in myocyte = myocardial depression

80
Q

how do halogenated agents affect HR

A

increased HR by desflurane, isoflurane, nitrous. no effect with ssevoflurane

-decreased SA node automaticity
-decreased conduction velocity through AV node, Purkinje fibers, ventricular conduction pathways
-increased duration of myocardial repolarization by impairing the outward current of potassium = increased QT interval due to prolonging AP
-altered baroreceptor function

81
Q

why do des and iso increase HR 5 - 10%

A

SNS activation from respiratory irritation

-ne release at b1

82
Q

how does nitrous oxide by itself affect hemodynamics

A

activates SNS.
increased MAP d/t increased SVR.

CVP may increase

also a myocardial depressant

83
Q

how do halogenated agents contribute to hypercarbia

A

drop Vt and increase RR
decrease Mve = increased Vd
-shifts CO2 response curve down and to the right
-impair genioglossus muscle and thoracic muscles (decreased FRC)

84
Q

what is CMRO2 a function of

A

60% = electrical activity
40% = homeostasis

85
Q

at what MAC does isoelectricity occur

A

1.5 - 2 MAC

VA uncouple CMRO2 and CBF!

86
Q

how do VA affect evoked potentials?

A

decrease amplitude
increase latency

87
Q

which potential is most sensitive to VA

A

visual evoked
BAER most resistant

APEX (18 decks)

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