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Medical Pharmacology > Pharmacology of Antimycobacterial/Antiprotozoal Agents > Flashcards

Pharmacology of Antimycobacterial/Antiprotozoal Agents Flashcards

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USMLE® Step 1 flashcards
1
Q

what is RIPE for TB?

A

rifampin, isoniazid, pyrazinamide/streptomycin, ethambutol

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2
Q

MOA of rifampin

A

inhibits transcription by binding to the Beta subunit of RNA polymerase, stopping phosphodiester bone formation in RNA

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3
Q

what are the rifamycins?

A

rifampin, rifabutin, rifapentine

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4
Q

MOA of rifamycins

A

form very stable complex with RNA polymerase to prevent elongation

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5
Q

spectrum of rifamycins

A

love to kill bacteria in the phagosome, very broad including mycobacteria, not enterobacteraceae

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6
Q

resistance against rifamycins

A

spontaneous mutation of rpoB gene (rapid and predictable)

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7
Q

use of rifamycins

A

monotherapy only for prophylaxis for neisseria meningitis or h influenzae meningitis, combination therapy for TB, leprosy, bone infections, endocarditis

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8
Q

ADE rifamycins

A

potent enzyme inducer so has many drug interactions, stains body fluids red/orange

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9
Q

what is izoniazid used for

A

used only for TB

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10
Q

what activates isoniazid

A

mycobacterial catalase-peroxidase

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11
Q

how does resistance occur against isoniazid

A

inactivation of catalase peroxidase via mutation of KatG gene

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12
Q

kinetics of isoniazid

A

N acetylation and hydroxylation, food decreases absorption

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13
Q

ADE of isoniazid

A
  1. hepatitis
  2. peripheral neuropathy (prevent with B6)
  3. lupus like syndrome (because slow acetylator)
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14
Q

which drugs are N acetylators

A

dapsone (sulfonamides), hydralazine, isoniazid, procainamide
(SHIP)

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15
Q

what is SLE like syndrome

A

when N acetylators are acetylated too slow and it looks like lupus

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16
Q

what is pyrazinamide

A

TB drug that inhibits bacterial FA synthetase I and reduce pH

rapidly cidal

ADE: hepatitis, gout, hematologic toxicity

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17
Q

what is streptomycin

A

aminoglycoside inhibition of protein via binding to 30S, misreading

ADE: nephrotoxic, ototoxic, neuromuscular blockade (not hepato!)

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18
Q

what is ethambutol

A

for TB and mycobacterium avium intracellulare (MAC)

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19
Q

MOA ethambutol

A

inhibits arabinosyl transferase, interfering with cell wall synthesis

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20
Q

ADE ethambutol

A

check to see colorblindness BEFORE, optic neuritis, colorblindness, hepatitis

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21
Q

what is used for intensive TB tx

A

2 months of RIPE

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22
Q

what is used for continuation phase for TB tx

A

4 months of INH plus rifampin

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23
Q

when to treat for TB

A
  1. 5mm induration with HIV, recent contact, old TB, organ transplant, immunocompromised
  2. 10mm induration IV drug user, recent immigrants, residents and employees of nursing homes, hospitals, correctional facility etc
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24
Q

what to use to treat latent TB?

A

isoniazid

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25
Q

what is MAC (mycobacterium avius intracellulare)

A

opportunistic pathogen in HIV most commonly seen when CD4 less than 50.

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26
Q

prophylaxis for MAC

A

azithromycin or clarithromycin

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27
Q

treatment for MAC

A

azithromycin or clarithromycin plus ethambutol and rifabutin

28
Q

how to treat mycobacterium leprae

A

dapsone
rifampin
clofazimine
thalidomide

29
Q

what does dapsone do

A

inhibits dihydropterate synthetase (loss mycobacterial folate)

30
Q

ADE dapsone

A

hemolysis in G6PD

31
Q

what is clofazimine

A

phenazine dye that reduces the risk of erythema nodosum leprosum

32
Q

what is thalidomide

A

treats erythema nodosum leprosum, multiple myeloma and mycobacterial infections – also teratogenic

33
Q

what is metronidazole used for

A

extraluminal amebiasis (kills trophozoites of enteramoeba histolytica .

also trichomoniasis
also giardia

also c diff but not anymore

34
Q

what activates metronidazole

A

pyruvate ferredoxin oxireductase (PFOR) to its active reduced form, bind DNA and proteins, leading to microbial death

35
Q

ade metronidazole

A

disulfram reaction

36
Q

what is most responsible for complications for malaria?

A

p falciparum (complications, death and drug resistance_

37
Q

malaria prophylaxis

A

prevent mosquito bites! increasing resistance means no chemoprophylactics are completely protective.

38
Q

what eradicates the hypnozoites from p vivax and ovale?

A

primaquine

39
Q

what do tissue schizonticides do

A

eliminate developing or dormant liver forms

40
Q

what do blood schizonticides do

A

act on erythrocytic parasites

41
Q

what do gametocides do

A

kill sexual stages to prevent transmission to mosquitos

42
Q

what does primaquine do

A

prevents relapses of vivax and ovale by killing hypnozoites – does not work on eyrthrocytic form

43
Q

when does primaquine reach peak?

A

1-2 hours

44
Q

ADE of primaquine

A

causes hemolytic anemia in G6PD , cannot be used in pregnancy

45
Q

which drugs cannot be used with G6PD

A

sulfonamides (dapsone)
primaquine
nitrofurantoin

46
Q

benefits of primaquine

A

good for last minute travelers bc started 1-2days before.

also most effective for vivax so good for travel where there is 90%+ vivax

47
Q

drawback of primaquine

A

no G6PD, not used for pregnant women

take it every day

48
Q

effectiveness of chloroquine

A

highly effective blood schizonticide, moderate against gametocyte of vivax, ovale, malariae, NOT falciparum

49
Q

drawback of chloroquine

A

resistance is common in falciparum

50
Q

advantage of chloroquine

A

taken weekly, can take if pregnant, good for long trips bc taken weekly

51
Q

disadvantage of chloroquine

A

cannot be used in areas with chloroquine or mefloquine resistance, may exacerbate psoriasis, must be started 1-2weeks before travel and taken 4 weeks after

52
Q

action of atovaquone and proguanil

A

atovaquone: disrupts mitochondrial electron transport
proguanil: converted to active metabolite that inhibits plasmodial dihydrofolate reductase

ARE ACTIVE AGAINST TISSUE AND ERYTHROCYTIC SCHIZONTS allowing chemo to be stopped 1 week after end of exposure

53
Q

benefit of atovaquone and proguanil

A

good for last min bc take 1-2days before, good for shorter trips bc taking only 1 week after traveling.

54
Q

drawback of atovaquone and proguanil

A

expensive, cannot be used by pregnant

55
Q

what is mefloquine

A

effective single agent for prophylaxis and treatment of infections caused by multidrug resistant forms of p falciparum

strong blood schizonticidal but not hepatic or gametocytes

56
Q

half life of mefloquine

A

20 days – weekly dosing, steady state over a number of WEEKS

57
Q

ade mefloquine

A

boxed warning of neuro and pyschiatric toxicities (appear in 50%)

don’t use with hx of epilepsy, psych disorders, arrythmia, cardiac conduction defects

58
Q

benefit of mefloquine

A

good for long trips because 1 weekly, can be used in pregnancy

59
Q

drawback mefloquine

A

not good for last minute, needs to be started at least 2 weeks before. must take 4 weeks after so not good for short trips.

60
Q

what is quinine

A

gametocidal against vivax and ovale not falciparum

61
Q

ADE quinine

A

tinnitus, HA, nausea, dizziness, flushing, visual disturbances == called cinchonism

62
Q

when is primethamine used

A

not widely used because of frequent resistance and toxicity

63
Q

what antibiotics are used for erythrocytic schizonts?

A

tetracycline and doxycycline, doxy has become standard chemoprophylactic esp in areas with high rates of resistance

64
Q

why is doxycycline good for travelers

A

last minute is good bc only 1-2 days before leaving, least expensive

65
Q

drawback of doxycycline

A

cannot use when pregnant

66
Q

what is nitazoxanide used for

A

giardia and cryptosporidium parvum

Medical Pharmacology (13 decks)

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