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Pharmacology Kaplan > Pharma General Principles > Flashcards

Pharma General Principles Flashcards

1
Q

permeation depends on

A
  • solubility (ionized are water soluble, unionized are lipid soluble)
  • conc gradient (only FREE and UNionized contribute)
  • SA and vascularity
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2
Q

some weak acid drugs

A
  • aspirin (ASA, acetyl salisylic acid)
  • penicillin
  • cephalosporins
  • loop & thiazide diuretics
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3
Q

some weak base drugs

A
  • morphine
  • local anesthetics
  • amphetamines
  • PCP (angel dust)
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4
Q

in which environment is a weak acid lipid soluble?

A

a weak acid is lipid soluble in an acidic environment (AH)

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5
Q

in which environment is a weak base lipid soluble?

A

a weak base is lipid soluble in a basic environment (B)

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6
Q

What forms of drug are filtered through the kidney?

A
  • both ionized and nonionized forms filtered but the drug MUST be FREE and UNBOUND
  • also note than ionized form is trapped in the filtrate b/c it’s NOT lipid soluble (whereas unionized can be reabsorbed or secreted b/c it is lipid soluble)
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7
Q

if overdose on weakly basic drug (ex: amphetamine, PCP), what should do?

A
  • acidify the urine to incr renal elimination (in an acid environ, a weak base is ionized and therefore water soluble and lipid insoluble)
  • can give vitamin C, cranberry juice, or the fav NH4Cl (ammonium chloride)
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8
Q

if overdose on weakly acidic drug (ex: aspirin), what should do?

A

alkalinize the urine (with NaHCO3 or acetazolamide) to incr renal elimin

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9
Q

NH4+ is

A

ammmonium

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10
Q

NH3 is

A

ammonia

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11
Q

fastest route of absorption

A

inhalation

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12
Q

bioavailability of IV admin drug

A

100%

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13
Q

bioavailability calculation

A

f = AUCpo/AUCiv (AUC = area under curve, f = bioavailability, po = per oral)

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14
Q

which a stronger barrier to distribution - placenta or blood-brain barrier?

A

BBB

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15
Q

BBB is only permeable to . . .

A
  • lipid soluble drugs

* very low mw drugs (ex: Li+, EtOH)

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16
Q

what kinds of drugs are safer during pregnancy?

A
  • water-soluble (b/c can’t cross membranes)
  • large
  • protein-bound
    (ex: choose PTU over methimazole b/c PTU more highly protein-bound; Phenobarbital safer anticonvulsant b/c highly protein-bound)
17
Q

volume distribution

A

Vd = Dose/Co (Co = plasma conc at time=0)

note L vs. L/kg . . . don’t forget to multiple by pt wt

18
Q

interpreting low v high volume distribution

A
  • low - lots of drug bound to plasma protein

* high - lots of drug sequestered in tissues

19
Q

effect of P450 inducers v. inhibitors

A
  • inducer –> incr P450 enzymes –> decr drug level in plasma (for certain drugs) therefore may need to give more drug
  • inhibitor –> decr P450 enzymes –> less metab –> risk of drug toxicity b/c incr drug level in plasma
20
Q

some classic P450 inducers?

A
  • phenobarbital
  • phenytoin
  • carbamazepine
  • rifampin
  • chronic alcohol
21
Q

some classic P450 inhibitors?

A
  • cimetidine (OTC med)
  • marcrolides (esp erythro-) . . .(note azythromycin is not a P450 inhibitor)
  • ketonconazole
  • “avirs” - antivirals, proteases for HIV
  • ACUTE alcohol
  • grapefruit juice
22
Q

Phase I Rxns

A

hydrolysis, oxidation (monoamine oxidase, CYP450), alcohol metabolism, reduction

23
Q

Phase II Rxns

A
    • conjugation rxns (endogenous compound is conjugated to a drug by a transferase)
  • includes glucuronidation, acetylation, GSH conjugation
24
Q

zero order kinetics

A

constant AMOUNT eliminated per unit time

* thus t1/2 is variable
ex: zero “peas” for me: phenytoin, EtOH, aspirin

25
Q

first order kinetics

A

constant FRACTION eliminated per unit time

t0.5 is constant (t0.5 = 0.7/k

26
Q

rate of elimination

A

rate of elimination = GFR + active secretion - reabsorption

27
Q

Clearance defn

A

volume of blood cleared of drug per unit time

constant in 1st order kinetics

28
Q

What is used to estimate GFR? Why?

A

inulin clearance (b/c inulin is neither secreted nor reabsorbed)

29
Q

equations for Clearance

A
  • Cl = free fraction x GFR (b/c protein-bound drug is NOT cleared)
    same as saying Cl = (1-% protein-bound)xGFR
30
Q

steady state

A

when rate in = rate out

31
Q

What does steady state depend on?

A

steady state depends on half-life (t0.5) ONLY

It does not depends on dose size and freq admin

32
Q

What does rate of infusion (Ko) determine?

A

plasma level at steady state (but NOT the time to reach steady state

33
Q

how do calculate time to clinical steady state?

A

4 or 5 time t1/2

34
Q

loading dose calculation

A

LD = (Cp x Vd)/f (Cp= conc in plasma, Vd= volume distribution, f=bioavailability)

35
Q

t1/2 eqn

A

t1/2 = (0.7 x Vd)/Cl

36
Q

infusion rate eqn

A

Ko = Cl x Css (Ko = infusion rate, Cl = clearance, Css = conc steady state)

37
Q

maintenance dose eqn

A

MD = (Cl x Css x dosing interval)/f (f=bioavail)

Pharmacology Kaplan (2 decks)

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