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Pharm test #3 > CEPHALOSPORINS > Flashcards

CEPHALOSPORINS Flashcards

1
Q

Cephalosporin chemical structure and significance

A

β-lactam ring with a 6-membered dihydrothiazine ring (PCN has a 5 membered ring).

provides stability against many β-lactamase enzymes that render the penicillins inactive

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2
Q

Cephamycins chemical structure and significance

A

methoxy group at position 7 of the β-lactam
ring

confers activity against anaerobes such as Bacteroides spp.

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3
Q

Mechanism of action of Cephalosporins

A

bind and inhibit PBPs which inhibits cell wall synthesis (inhibit cross-linking)

same as penicillins

Bactericidal

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4
Q

3 mechanisms of resistance to cephalosporins

A
  1. β-lactamase enzymes (most common, hydrolyzes the bond of the β-lactam ring)
  2. altered PBPs
  3. altered permeability
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5
Q

Which cephalosporins have the most β-lactamase resistance

A

3rd and 4th generations

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6
Q

SPICE bacteria

A

have the ability to produce β-lactamase enzymes when exposed to antibiotics that induce their production (inducable β-lactamases)

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7
Q

1st generation cephalosporins have activity against

A

many gram positive aerobes (the best of all cephalosporins) and some gram negative aerobes

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8
Q

gram positive bacteria that 1st generation cephalosporins have activity against

A

MSSA
penicillin-susceptible S. pneumoniae
group A and B streptococcus
viridans streptococci

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9
Q

gram negative bacteria that 1st generation cephalosporins are active against

A

PEK
Proteus mirabillis
E. coli
Klebsiella pneumoniae

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10
Q

2nd generation cephalosporin activity

A

slightly less active against gram + when compared to 1st generation.

but more active against gram negative aerobes and cephamycins have anaerobe activity

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11
Q

gram negative aerobes that 2nd generation cephalosporins have activity against

A 
HENPEK
Haemophilus influenza
Morazella catarrhalis
Enterobacter
Neisseria spp. 
P. mirabillis
E. coli
K. pneumoniae
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12
Q

cephamycin activity

A

same as the other 2nd generation cephalosporins with additional activity against some anaerobes including Bacteroides fragilis

ie cefoxitin

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13
Q

3rd generation cephalosporin activity

A

generally less gram + than 1st and 2nd gen. but expanded gram negative aerobe activity

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14
Q

ceftriaxone is what generation

A

3rd generation

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15
Q

ceftriaxone and cefotaxime are one of the only cephalosporins with activity aginst

A

penicillin resistant S. pneumoniae

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16
Q

gram negative coverage for 3rd generation cephalosporins

A

HENPECKSSS (and more)
P. mirabilis, E. coli, K. pneumoniae
H. influenzae, M. catarrhalis, Neisseria gonorrhoeae (even β-
lactamase producing strains)
Neisseria meningitidis
Citrobacter spp., Enterobacter spp. (less with oral agents)
Morganella spp., Providencia spp.,

Serratia marcescens, Salmonella spp., Shigella spp.

Pseudomonas aeruginosa - only ceftazidime and cefoperazone

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17
Q

which 3rd generation cephalosporins have activity against Pseudomonas aeruginosa

A

only ceftazidime and cefoperazone

not ceftriaxone

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18
Q

which generation has some strong inducers of extended spectrum β-lactamases

A

3rd generation

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19
Q

4th generation of cephalopsorins

A

extended spectrum of activity for many gram positive and negative aerobes (no anaerobes)

excellent stability against β-lactamases hydrolysis and is a poor inducer of ESBL

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20
Q

cefepime is given

A

via IV only

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21
Q

gram negative coverage of 4th generations

A

similar to 3rd generation including
Pseudomonas aeruginosa and
β-lactamase producing Enterobacter and E. coli

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22
Q

Cephalosporins are NOT active against

A 
methicillin-resistant Staphylococcus
aureus (MRSA) 
coagulase-negative staphylococci, Enterococcus spp., 
Listeria monocytogenes, 
Legionella pneumophila, 
Clostridium difficile, 
Stenotrophomonas maltophilia, and
 Campylobacter jejuni.
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23
Q

cephalosporins absorption

A

well absorbed but have low serum concentrations when given orally.

Food affects the absorption

24
Q

cephalosporin distribution

A

most are widely distributed except 1st and 2nd generations do not achieve adequate CSF concentrations

25
Q

cephalosporin elimination

A

mostly eliminated unchanged by the kidneys

must adjust the dose in the presence of renal insufficiency

• exceptions: ceftriaxone - bilary system, and cefoperazone - liver

26
Q

cephalosporin half lives

A

most are short - need multiple doses per day, exceptions include: ceftriaxone which has an 8 hr half-life

27
Q

clinical uses for 1st generation cephalosporins

A

Skin and soft tissue infections, septic arthritis, osteomyelitis, endocarditis, surgical prophylaxis*, urinary tract infections, bacteremia

28
Q

clinical uses for 2nd generation cephalosporins

A
  • Sinusitis, otitis media, upper and lower respiratory tract infections
  • Polymicrobial infections or surgical prophylaxis for abdominal surgery – (cephamycins - cefoxitin, cefotetan)
29
Q

clinical uses for 3nd generation cephalosporins

A
  • Bacteremia, pneumonia, complicated urinary tract infections, peritonitis, intra-abdominal infections, skin and soft tissue infections, bone and joint infections, meningitis**
  • Ceftriaxone is used for uncomplicated gonorrhea (single IM dose), CAP, PRSP, viridans strep endocard
30
Q

what would you use for a meningitis where Pseudomonas was suspected

A

ceftazidime or a 4th generation (cefepime)

31
Q

clinical uses for 4th generation cephalosporins

A
  • Pneumonia, bacteremia, urinary tract infections, skin and soft tissue infections, intraabdominal infections, Gram-negative meningitis, febrile neutropenia
  • Covers Pseudomonas**
32
Q

clinical uses for 5th generation cephalosporins

A

Community acquired bacterial pneumonia

Skin and skin structure infections

33
Q

adverse effects of cephalosporins

A
  • hypersensitivity (up to 15% of pts w/ pcn allergies)
  • MTT side chain
  • Hematologic - leukopenia, thrombocytopenia
  • GI - ↑ bili; C. difficile colitis
  • IV calcium and ceftriaxone precipitates, cefepime/ceftaz and nonconvulsive status epilepticus
34
Q

MTT side chain

A
  • Hypoprothrombinemia - due to enzyme inhibition of vitamin K metabolism or reduction in vitamin K-producing bacteria in GI tract (impaired blood clotting)
  • Ethanol intolerance (inhibits alcohol dehydrogenase)
35
Q

Carbapenems (4 of them)

A

imipenem, meropenem, erta-penem, and doripenem

36
Q

Carbapenems primary binding target

A

PBP-2

37
Q

carbapenems mechanism of action

A

bactericidal - time depended

inhibits cell wall synthesis

38
Q

carbapenems mechanisms of resistance

A

β-lactamase production, decreased permeability, alteration in PBPs

39
Q

carbapenems spectrum of activity

A
  • most broad specturm agents available **

* Have activity against gram-positive and gram-negative aerobes AND anaerobes

40
Q

bacteria NOT covered by carbapenems

A

MRSA, PRSP, VRE, coagulase-negative staph, C. difficile, atypical bacteria, S. maltophilia,

41
Q

which carbapenems have the greatest spectrums of activity

A

imipenem, and doripenem

42
Q

pseudomonas aeruginosa is killed by which carbapenems

A

imipenem, meropenem, and doripenem

NOT ERTAPENEM

43
Q

which carbapenem has the best CSF penetration?

A

meropenem

44
Q

how are carbapenems eliminated

A
  • kidney (need dosage adjustment with renal dysfunction)
  • Imipenem undergoes hydrolysis by a dihydropeptidase enzyme in the renal brush border to a nephrotoxic metabolite; comarketed with cilastatin, a DHP inhibitor (otherwise it would be cleared too quickly)
  • Short elimination half-lives (ertapenem 4 hours- longest can be given once a day)
45
Q

what is impenem is always given with

A

cilastatin (inhibits DHP which would otherwise inactivate impenem)

46
Q

clinical uses of carbapenems

A
  • Empiric therapy for hospital acquired infections
  • Polymicrobial infections (broad spec)
  • Infections due to β-lactamase-producing organisms (SPICE, SPACE, others)
  • Febrile neutropenia – imip and mero
  • Meningitis – meropenem
  • If Pseudomonas is known or suspected – NOT ertapenem**
47
Q

adverse effects of carbapenems

A
  • hypersensitivity (cross-reactive w/ pcn)
  • GI
  • CNS - Confusion, dizziness, hallucinations, seizures. Risk factors for seizures include preexisting CNS disorder, high doses, renal insufficiency
48
Q

Monobactam drug name

A

Aztreonam is the only monobactam currently available

49
Q

Monobactam preferred binding target

A

PBP-3 of gram negative aerobes - inhibits cell wall synthesis like other β-lactams

50
Q

monobactams are affective against

A

Gram-Negative Aerobes ONLY
E. coli, K. pneumoniae, P. mirabilis, S. marcescens, H. influenzae, M. catarrhalis, Enterobacter, Citrobacter, Providencia, Morganella, Salmonella, Shigella, Pseudomonas aeruginosa**

51
Q

Monobactams (Aztreonam)
 distribution

A

only available IV
Widely distributed into body tissues and fluids
Penetrates the CSF in the presence of inflamed meninges

52
Q

Monobactams (Aztreonam) Elimination

A
  • Excreted in the urine as unchanged drug
  • Short elimination half-life of 1.3 to 2.2 hours
  • Doses need adjustment with renal dysfunction; is removed by hemodialysis
53
Q

Aztreonam clinical uses

A

Clinical uses include urinary tract infections, respiratory tract infections, meningitis, bacteremia, skin and soft tissue infections, and intraabdominal infections due to susceptible gram-negative aerobes

54
Q

Aztreonam adverse effects

A
  • Gastrointestinal: nausea, diarrhea

* Hypersensitivity: no cross-reactivity with penicillins, can be used in penicillin-allergic patients

55
Q

what would you give to a pt with a suspected gram negative infection who is allergic to penicillin?

A

aztreonam - no cross-reactivity w/ pcn

Pharm test #3 (17 decks)

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