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D&D Infectious Disease Midterm > Pharm - Sulfonamides, Trimethoprim (Nuc. Acid. Synth. Inhibitors) > Flashcards

Pharm - Sulfonamides, Trimethoprim (Nuc. Acid. Synth. Inhibitors) Flashcards

1
Q

what is the most COMMON bacterial cause of UTI

A

e. coli

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2
Q

protonsil was first discovered to work in a 10 month old infant with what infection

A

staphylococcal septicemia

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3
Q

name 3 “general purpose” sulfonamides

A

sulfamethoxazole
sulfadiazine
sulfisoxazole

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4
Q

name 3 sulfonamides for special applications

A

mafenide
silver sulfadiazine
sulfacetamide sodium (ophthalmic)

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5
Q

true or false

trimethoprim is available both on its own and as a combination with sulfamethoxazole

A

true

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6
Q

aside from sulfonamides and trimethoprim, name another chemical class that are nucleic acid synthesis inhibitors

A

pyrimethamine

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7
Q

how is pyrimethamine available

A

by itself and in combination with sulfadoxine

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8
Q

true or false

trimethoprim and pyrimethamine by themselves do not contain sulfa

A

true

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9
Q

all the sulfas are derived from what molecule and what molecule does this mimic

A

SULFANILAMIDE - which structurally mimics PABA — the starting point of nucleic acid synthesis

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10
Q

true or false

sulfa drugs are noncompetitive inhibitors of PAPA

A

FALSE - competitive

they are structurally similar - only diff is that the COOH in PABA has been chaned to sulfonamide in sulfanilamide

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11
Q

differentiate between what they inhibit:

sulfonamides vs trimethoprim and pyrimethamine

A

sulfonamides inhibit DHPS (dihydropteroate synthase)

trimethoprim and pyrimethamine inhibit DHFR (dihydrofolate reductase)

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12
Q

true or false

trimethoprim and pyrimethamine are competitive inhibitors

A

true - structually analgous to the substrate of DHFR

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13
Q

sulfonamides are structurally analagous to ______ and inhibit ______

A

PABA

inhibit dihydropteroate synthase

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14
Q

sulfonamides have synergy with……..

A

DHFR inhibitors
(trimethoprim and pyrimethamine)

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15
Q

bacteria need to synthesize _____ for nucleic acid biosynthesis

A

folate

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16
Q

explain the mechanism of purine (produces DNA) synthesis

include enzymes, cofactors, and which steps are inhibited

A

Pterdine + PABA gives dihydropteroic acid through dihydropteroate synthase
(THIS IS THE STEP THAT SULFONAMIDES INHIBIT)

dihydropteroic acid and glutamate as cofactor give dihydrofolic acid (enzyme = dihydrofolate synthase)

dihydrofolic acid with NADPH as cofactor (oxidized to NADH) and through DHFR produces THF (tetrahydrofolic acid)

THF produces purines and then DNA

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17
Q

of the 3 enzymes involved in bacterial DNA (nucleic acid) synthesis, which do humans have? explain

A

we have dihydrofolate synthase – that’s why it’s not a target for antibiotics

however, we also have DHFR, HOWEVER, this is still a target for trimethoprim!!!!! this is possible because trimethoprim and pyrimethamine have much higher affinity for the bacterial version of the enzyme rather than the human version

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18
Q

what does methotrexate inhibit

A

DHFR (OF HUMANS)

19
Q

are sulfonamides bacteriostatic or cidal

A

static

20
Q

true or false

sulfonamides are active against gram positive and gram negative bacteria

A

TRUE - but there are exceptions

not effective against the gram negative pseudomonas aeruginosa (resistant)

actually STIMULATES the growth of the gram positive - rickettsiae

21
Q

true or false

sulfonamides have activity against anaerobes

A

FALSE - very poor activity

22
Q

are sulfonamides active against enteric bacteria? how can you remember this?

A

YES
remember - can be used for UTI which is mainly due to e. coli

HOWEVER, some strains of e. coli, neisseria, and shigella are resistant - watch out

23
Q

name 3 main infections that bactrim is used for

A

UTI
respiratory tract pathogens
ear infections

24
Q

true or false

bactrim is effective against both MRSA and MSSA strains

A

true

25
Q

are sulfonamides active against protozoa?

A

some

26
Q

name 4 main mechanisms in which bacteria become resistant to sulfonamides

A

overproduce PABA - which competes with sulfa

overproduce dihydropteroate synthase

impair permeability, or actively efflux the sulfonamide

some bacteria use EXOGENEOUS folate - intrinsically resistant bc they don’t need that first step anymore that sulfonamides inhibit

27
Q

4 methods of trimethoprim resistance

A

reduce cell permeability (gram -)

overproduce DHFR

produce an ALTERED reductase enzyme so the drug has reduced binding

by mutation or plasma-encoded trimethoprim resistant DHFR’s

28
Q

bactrim is the drug of choice for which 3 infections??

why isn’t it used more?

A

UTI
MRSA
ear infections in kids

not used as much bc of development of resistance

29
Q

sulfa______ and sulfamethoxazole are used almost exclusively to treat UTIS

A

sulfasoxazole

30
Q

_________ is widely used in ulcerative colitis, enteritis, and other IBD’s, and rheumatoid arthritis

A

sulfasalazine

31
Q

________ is used as ophthalmic solution or ointment for bacterial conjunctivitis and trachoma

A

sodium sulfacetamide

32
Q

___ and ___ are used topically for burn wounds

A

silver sulfadiazine and mafenide acetate

33
Q

sulfasalazine is oral, but is it absorbable or nonabsorbable

A

non

34
Q

__+ ___ is first line therapy for acute toxoplasmosis

A

sulfadiazine + pyrimethamine

35
Q

long acting oral absorbable sulfonamide and what used for

A

sulfadoxine

sulfadozine + pyimethamine used for malaria (NOT IN US)

36
Q

how is trimethoprim excreted and why is this important

A

most is excreted unchanged in the urine (only 30% metabolized) – thus, kidney function is very important

if low function, need to decrease dose

37
Q

explain how sulfonamides are distributed and excreted

A

widely distributed - CNS, placenta, fetus

excreted in the URINE in both free and acetylated forms

38
Q

which sulfonamide has an EXTREMELY long half life of 4-10 days

A

the long acting - sulfadoxine

39
Q

important adverse effects of sulfonamides

A

SJS (RARE)
mild rashes
photosensitivity
NVD
in pts with G6PDH deficiency - hemolytic anemia
CNS effects (headache, delirium)
UT - crystalluria and hematuria

40
Q

name for sulfonamide metabolites

A

haptens

41
Q

sulfa POTENTIATES these drugs……

explain

A

oral anticoagulants
sulfonylurea hypoglycemics
hydantoin anticonvulsants

displaces them from albumin and inhibits their metabolism, thus INCREASING their effect (potentiation)

42
Q

trimethoprim AE

A

megaloblastic anemia
leukopenia
granulocytopenia
bone marrow suppression

43
Q

in pts with AIDS and pneumocystic pneumonia, what toxicity can occur

A

liver

44
Q
A

D&D Infectious Disease Midterm (26 decks)

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