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Antibiotics > Cephalosporins > Flashcards

Cephalosporins Flashcards

1
Q

Cephalosporin General Facts

A

Have some cross allergenicity with penicillins
Cross reactivity quoted at 10% but reasonable estimate is 3-5% but less for later generations
Be skeptical of nausea
Take hives and anaphylaxis seriously
Similar side chains may be responsible for cross reactivity

Generally more resistant to betalactamses than penicillins
Cephalosporinases exist and are becoming more prevalent (in contrast to penicillinases)

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2
Q

First Generation Cephalosporins

A

Oral
Cephalexin
Cefadroxil

IV
Cefazolin
Cephalothin

Used immediately prior to surgery to prevent surgical site infections; most commonly used class in the hospital
Ideal because of spectrum, cheap, low incidence of adverse effects
Useful for treating skin and skin structure infections
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3
Q

First Generation Cephalosporins Spectrum

A

Good
MSSA
Streptococci

Moderate
Some enteric GNRs

Poor 
Enterococci
Anaerobes
MRSA 
Pseudomonas
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4
Q

First Generation Cephalosporins Important Facts

A

Good alternatives to antistaphylococcal penicillins
Cause less phlebitis; infused less frequently
Unlike them, may not cross the blood brain barrier;
Should not be used in CNS infections

Good for 
Skin and skin structure infections
Surgical prophylaxis (usually should not give more than one dose; giving more than 24 hours of therapy is rarely justified-does not lower infection rates but may select for more resistant organisms later in the hospital stay)
Staphylococcal bloodstream infections
Osteomyelitis 
Endocarditis (MSSA)
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5
Q

Second Generation Cephalosporins

A

Oral
Cefaclor
Cefprozil
Loracarbef

IV
Cefoxitin 
Cefotetan
Cefmetazole
Cefonicid
Cefamandole

Oral and IV
Cefuroxime

Better Gram- activity; somewhat weaker Gram+ activity but still used for these organisms

More stable against Gram- betalactamases and particular active against H. influenzae and N. gonorrhoeae

Most numerous cephalosporins but least utilized in the US

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6
Q

Second Generation Cephalosporins Spectrum

A

Good
Some enteric GNRs
Haemophilus
Neisseria

Moderate
Streptococci
Staphylococci
Anaerobes (only cefmetazole, cefotetan, cefoxitin)

Poor
enterococci
MRSA
Pseudomonas

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7
Q

Second Generation Cephalosporins Adverse Effects

A

Ceph with N-methylthiotetrazole (MTT) side chain can inhibit vitamin K production and prolong bleeding (cefmetazole, cefotetan, cefamandole)
Can also cause a disulfiram like reaction when given ethanol

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8
Q

Second Generation Cephalosporins Important Facts

A

Cephamycins (cefmetazole, cefotetan, cefoxitin)
Have activity against many anaerobes in GI tract
Cefoxitin and Cefotetan often used for surgical prophylaxis in abdominal surgery

Loracarbef is a carbacepbem

Do not cross the blood brain barrier well enough to be used in CNS infections (like the first gen ceph)

Good for 
Upper respiratory tract infections
Community acquired pneumonia
Gonorrhea
Surgical prophylaxis (cephamycins)

Cephamycins have good intrinsic anaerobic activity but resistance is increasing in Bacteroides fragilis group infections
In surgical prophylaxis, limit duration after surgery
If infection develops, use an alternative (beta lactamase inhibitor combination or another Gram- agent with metronidazole)

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9
Q

Third Generation Cephalosporins

A

Greater Gram- coverage than 1G and 2G

Good strep activity but less staph than previous generations

Considered broad spectrum agents

Ceftriaxone 
Cefotaxime
Ceftazidime
Cefdinir
Cefpodoxime
Cefixime
Ceftibuten
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10
Q

Third Generation Cephalosporins Spectrum

A

Good
Streptococci (ceftazidime is poor)
Enteric GNRs
Pseudomonas (only ceftazidime)

Moderate
MSSA (ceftazidime is poor)

Poor 
Enterococci 
Pseudomonas (except ceftazidime)
Anaerobes 
MRSA
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11
Q

Third Generation Cephalosporins Adverse Effects

A

One of the classes with strongest association with Clostridium difficile associated diarrhea

Cefpodoxime has MTT side chain that can inhibit vitamin K production

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12
Q

Third Generation Cephalosporins Important Facts

A

Ceftazidime is unique
Is antipseudomonal
Lacks clinically useful activity against Gram+ organisms

Ceftriaxone, cefotaxime, ceftazidime cross the blood brain barrier effectively
Useful for CNS infections
Don’t use ceftazidime for community acquired meningitis where S. Pneumoniae predominates

Notorious for inducing resistance among GNRs
Too much broad spectrum usage can result in harder to treat infections

Ceftriaxone one time IM dose increased from 125 to 250mg for gonnorhea (drug of choice)
Should also receive azithromycin (empiric therapy for chlamydia and may reduce emergence of ceftriaxone resistance

Ceftriaxone has dual modes of elimination (renal and biliary excretion)
Does not need to renally adjusted but does effectively treat UTIs

Cefotaxime is safer than ceftriaxone for neonate for two reasons

  1. Interacts with calcium containing medications to form crystals; can precipitate in lungs and kidneys leading to fatalities
  2. Can lead to biliary sludging with resultant hyperbilirubinemia

Give higher doses of ceftriaxone (2-4g per day) for MSSA (especially invasive infections)
Need higher doses due to less activity against this organism

Ceftriaxone is a once daily drug for almost all indications except meningitis
2g IV q12H
High dose used for meningitis mainly and a few more indications
Use vancomycin and ampicillin if indicated

Good for
Lower respiratory tract infections 
Pyelonephritis
Nosocomial infections (ceftazidime)
Lyme disease (ceftriaxone)
Meningitis
Gonorrhea
Skin and skin structure infections
Febrile neutropenia (ceftazidime)
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13
Q

Fourth Generation Cephalosporins

A

Cefepime

Broadest spectrum ceph

Cefazolin (1st) + Ceftazidime (3rd) = Cefepime (4th)

Has activity against Gram- (including Pseudomonas) and Gram+ organisms

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14
Q

Fourth Generation Cephalosporins Spectrum

A 
Good
MSSA
Streptococci
Pseudomonas
Enteric GNRs

Moderate
Acinetobacter

Poor
Enterococci
Anaerobes
MRSA

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15
Q

Fourth Generation Cephalosporins Important Facts

A

May be associated with more neurotoxicity compared with other agents
May manifest as nonconvulsive status epilepticus
Can occur at any dose; still need to adjust dose in renal dysfunction

Good empiric choice for many nosocomial infections; overkill for community acquired infections
Deescalate if possible

Cefepime is better choice than ceftazidime for mono therapy of febrile neutropenia
Better Gram+ activity
May induce less resistance in GNRs

Initially meta analysis showed increased mortality compared with other drugs
FDA exonerated it

Good for
Febrile neutropenia
Nosocomial pneumonia
Postneurosurgical meningitis 
Other nosocomial infections

Used primarily for nosocomial infections
Overkill for community acquired urinary tract and lower respiratory tract infections

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16
Q

Fifth Generation Cephalosporins

A

Ceftaroline

Anti-MRSA cephalosporin
Binds to the penicillin binding protein 2a of MRSA that has low affinity for other beta lactams

Has modest activity against E. faecalis

Less Gram- activity than Cefepime; similar to Ceftriaxone

Similar drug Ceftobiprole was removed from market

17
Q

Fifth Generation Cephalosporins Spectrum

A

Good
MSSA; MRSA
Streptococci
Enteric GNRs

Moderate
E. faecalis

Poor
P. aeruginosa 
E. faecium
Acinetobacter
Anaerobes
18
Q

Fifth Generation Cephalosporins Important Facts

A

Initial indications for new drugs are usually low hanging fruit: skin and skin structure, community acquired pneumonia; other agents available
However did outperform Ceftriaxone in 2 of 3 studies in CA-pneumonia

Case series and retrospective studies have shown it to be successful in bloodstream infections, endocarditis, meningitis, osteomyelitis, HA-pneumonia

Approved for treatment of complicated skin and soft tissue infections
CA-pneumonia

19
Q

Cephalosporin/Betalactamase Inhibitor Combinations

A

Ceftazidime/Avibactam
Ceftolozane/Tazobactam

Carbapenem resistance mostly seen in 3 organisms
Klebsiella pneumoniae
P. aeruginosa
A. baumannii

Avibactam is new kind of inhibitor; does not structurally resemble a beta lactam but binds to ases and makes them inert
Works against many ases produced by K. pneumo and P. aeruginosa
Restores activity of ceftazidime against many of these organisms

Ceftolozane is 3G ceph; evades many resistance mechanisms of P. aeruginosa

Neither of these drugs is good against Acinetobacter

20
Q

Cephalosporin/Betalactamase Inhibitor Combinations Spectrum

A 
Good
Pseudomonas
Enteric GNRs (ceftazidime/av > ceftolozane/tazo)
Moderate
Some streptococci (ceftolozane/tazo)

Poor
Most Anaerobes
MRSA/MSSA
Acinetobacter

21
Q

Cephalosporin/Betalactamase Inhibitor Combinations Important Facts

A

Both active against multi-drug resistant Pseudomonas
Only ceftazidime/avi active against carbapenem resistant Klebsiella and other enteric GNRs

Ceftolozane is minimally affected by many Pseudomonas resistance mechanisms including its ases; Tazobactam does little for this bug

Ceftazidime/avi relies on avi to inactivate Pesudomonas ases

Isolates of Pseudomonas may be resistant to one drug but susceptible to the other

There is substantial resistance to these agents by gut anaerobes unlike penicillin based beta lactamase inhibitors
If anaerobic involvement is suspected while on one of these agents, add metronidazole

Both good for
multi drug resistant Pseudomonas infections
Mixed aerobic/anaerobic infections
Infections caused by ESBL producing organisms
Intra-abdominal infections

Only Ceftazidime/avi
Carbapenem resistant Enterobacteriaceae infections

22
Q

Carbapenems

A

Broadest spectrum agents

Have a beta lactam ring but are structurally different and unique from penicillins and cephs

Imipenem, Doripenem, and Meropenem have similar spectra

Ertapenem has important differences

23
Q

Carbapenems Spectrum

A 
Good
MSSA
Streptococci
Anaerobes
Enteric GNRs 
Pseudomonas and Acinetobacter (not Ertapenem)
ESBL producing GNRs

Moderate
Enterococci (not Ertapenem)

Poor
MRSA
Penicillin resistant Streptococci

24
Q

Carbapenems Important Facts

A

Imipenem has higher propensity to induce seizures (calculate appropriate doses in renal dysfunction; avoid in patient with meningitis- it can cross blood brain barrier more readily)

Imipenem is metabolized in kidney to a nephrotoxic product
Cilastatin blocks the renal dehydropeptidase that catalyze a this reaction and prevents the metabolism from occurring
I-C always coadministered together

Good choices for nosocomial infections, especially people who have received many other classes of antibiotics during their hospital stay

Ertapenem is the exception; poor choice for many nosocomial infections:
Nosocomial pneumonia where Pseudomonas and Acinetobacter are important pathogens
However, administered only once a day; may be a better choice for home infusion therapy for susceptible infections

May uncommonly elicit an allergic reaction in patients with a history of penicillin allergy
Cross reactivity most likely around 1%
Patients with a history of allergy to any drug are more likely to react to another one even if unrelated

CarbapenemASES are becoming more common
Most common in NE US; very common in some parts of the world

All good for
Mixed aerobic / anaerobic infections
Infections caused by ESBL producing organisms
Intra-abdominal infections

All except Ertapenem
Nosocomial pneumonia
Febrile neutropenia
Other nosocomial infections

25
Q

Monobactams

A

Aztreonam

Only contains the four membered ring of the basic beta lactam structure

Seems to be safe to administer to patients with allergies to other beta lactams, except a specific allergy to ceftazidime
Both drugs share an identical side chain and spectra of activity (ceftolozane also has the side chain)

26
Q

Monobactams Spectrum

A

Good
Pseudomonas
Most GNRs

Moderate
Acinetobacter

Poor
Gram+ organisms
Anaerobes

27
Q

Monobactams Important Facts

A

Shares MOA and pharmacodynamic profile with other beta lactams
Often gets confused with aminoglycosides because of its spectrum; chemically unrelated and does not share their toxicities

Can be administered via inhalation in CF to prevent exacerbations of infection

Combining with other beta lactams not useful
Add a non beta lactam to empiric regimen for serious nosocomial infections

Good for
Gram- infections including Pseudomonas, especially in patients with history of beta lactam allergy

Antibiotics (63 decks)

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