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Pharmacology > Antibacterial drugs > Flashcards

Antibacterial drugs Flashcards

1
Q

what color are G+

A

dark purple

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2
Q

what color are G-

A

light pink

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3
Q

difference between G+ and G- bacteria

A

G+ have one bacterial cell membrane

G- have cell membrane-> inner and outer

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4
Q

can drugs penetrate G+ bacteria?

A

yes

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5
Q

can drugs penetrate G- bacteria?

A

Not readily

-must go through channels called porins

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6
Q

is the peptigoglycan layer thick or thin in G+

A

thick

-G- is thin

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7
Q

where are the beta-lactamases in G-?

A

in the periplasmic layer

-in G+, free

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8
Q

what is the difference between peptidogylcan structure in G+ and G-

A

G - have meso-diaminopimetic acid

G+ that group is a lysiene

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9
Q

in G- cells, what happens to peptidogylcan?

A

cross-linking by a bridge between the DAP residue of one strand and the terminal D-Ala of another

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10
Q

what is the cross-linking done by?

A

transpeptidase

  • attacks carbonyl-> forms tetrahedral intermediate (unstable)
  • peptidogylcan is linked via an ester bond-> then attacked by amine-> another tetrahedral intermediate-> linked peptidogylcan
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11
Q

beta-lactam MOA

A

acylate the transpeptidase ser residue in the enzyme active site to form a stable product-> inactivates enzyme, inhibiting peptidoglycan cross-linking-> results in a defective bacterial cell wall-> osmotic cell stress-> cell lysis and cell death.

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12
Q

why is beta-lactam so reactive?

A
  1. ) ring strain, carbonyl angle is 90 degrees
  2. ) folded ring structure N lone pair does not overlap with C=O, more reactive carbonyl because more like ketone than an amide carbonyl
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13
Q

resistance mechanism

A

mutation of penicillin binding protein
antibiotics are pumped out of cell
production of beta-lactamases
decreased cellular uptake of drug

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14
Q

what is an important characteristic of beta-lactamases activity?

A

hydrolysis of acylated beta-lactamase intermediate is very fast
-enzyme can hydrolyze many drug molecules quickly

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15
Q

where does the beta-lactam act for those who are allergic?

A

drug acts as a hapten

-acylates host cell proteins, which then raise antibiotics and results in an allergic reaction

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16
Q

test for penicillin allergy

A

topical flare and wheal test

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17
Q

how is penicillin degraded?

A

in acidic conditions and basic conditions

18
Q

how do you determine if penicillin will be degraded in acidic or basic conditions

A

electronegativity of R group on penicillin
-Pen G->has carbon-> carbonyl is more reaction
Pen V: has an O-> pulls electron density away from the carbonyl-> less reactive in stomach

19
Q

what should penicillin solutions be kept away from

A

heavy metal ions (catalyze penicillin degradation)

20
Q

serum protein binding: Penicillin

A

more lipophilic side chains-> more highly protein bound

21
Q

what does protein binding do to penicillin bioavailablity?

A

decreases it

-reduces effective concentration of free drug

22
Q

what is co-administered with penicillin to prolong half life?

A

probenecid

-competes for tubular secretion with penicillin-> increases its half-life, both are anionic

23
Q

is Benzylpenicillin (Pen G) beta-lactamase sensitive?

A

yes
Drug of choice for treating infections
-neisseria, hem. Influenza
- acute allergic reactions

24
Q

is Methicillin beta-lactamase sensitive?

A

No

-b/c of steric hinderance of nucleophilic attack by the enzyme on the beta-lactam carbonyl

25
Q

why doesn’t methicillin administered orally?

A

unstable in acid stomach-> must be injected
-instability due to electron donation toward the amide carbonyl oxygen by the methoxy groups-> makes amide carbonyl oxygen more reactive

26
Q

Cephapirin

A

cephalosporin antibiotic

  • six membered sulfur containing ring fused with beta-lactam
  • same MOA of penicillin
  • beta-lactamase sensitive
27
Q

how are Cephalosporins made inactive?

A

if have an acetate in 3-position are metabolically inactivated by hydrolysis of acetate by host esterase-> hydroxymethyl acid that lactonizes

28
Q

imipenem

A

carbapenems, carbon analogs of penicillin

  • inhitbit beta-lactamase
  • used for G+ and G-
29
Q

why is ring strain greater in carbapenems like impenem

A

sulfur is present in thiazolidine ring is a methylene group-> increases reactivity b/c methylene is smaller than sulfur

30
Q

what is imipenem co-administered with?

A

cilastatin sodium

-imipenem is hydrolyzed by renal dehydropeptiase-1 and this blocks that

31
Q

how is imipenem and cilastatin sodium administered?

A

parenterally

-infections of gut, GU tract, bone, skin and endocardium

32
Q

Aztreonam

A

synthetic

-inspired by monocyclic beta-lactam natural products called monobactams

33
Q

what is aztreonam used for?

A

G- bacteria, especially those by penicillin resistant organisms acquired in hospitals

34
Q

cross allergenicity has been seen with penicillins and cephalosporins with what antibiotic?

A

ceftazidime

35
Q

what is the main difference between aztreonam and penicillins/cephalosporins?

A

has a sulfamic acid group instead of carboxyl group

36
Q

Penicillin V

A

more stable to hydrolysis in stomach than Pen G because electronegativity of the ether oxygen decreases the nucleophilicity of the amide carbonyl

37
Q

What does protein binding do for penicillin

A

Protects from degradation

38
Q

Why aren’t the half life’s of penicillin affected by protein binding?

A
  1. Dissociate from protein fast

2. Renal excretion rates are rate limiting

39
Q

More lipophilic side chains mew what for penicillin

A

More highly protein bound

40
Q

Who should avoid taking Pen G

A

Histories of significant allergies or asthma

41
Q

Methicillin can treat

A

Staph aureus

Not MRSA tho

42
Q

What causes aztreonam to be more reactive with penicillin binding proteins?

A

Electro negativity of sulfamic acid activates the beta-lactam ring toward hydrolysis and to reaction with penicillin binding proteins

Pharmacology (14 decks)

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