Exam 7: Cephalosporins Flashcards
2 First Gen Cephalosporins
Cefazolin
Cephalexin
Most of them have a “ph” in their name.
4 Second Gen Cephalosporins
Cefaclor Cefoxitin Cefuroxime Cefprozil The FAM(ily) is gathered, some wearing FUR coats, and your FOX(y) cousin is drinking TE(a) and taking PRO(zac) while driving her CAR. It’s Nic(e) to have Met(life) insurance. Sweet Jesus.
4 Third Gen Cephalosporins
Ceftriaxone Cefixime Ceftaxime Ceftazidime Most have a T in their name except for the "fix" one (you have to FIX the car you drove in the second generation mnemonic)
4th Gen Cephalosporin
Cefepime
5th Gen Cephalosporin
Ceftaroline
What structural feature do Cephalosporins share with Penicillins?
Beta Lactam Rings
How can we change Cephalosporin structure to affect function?
changes are R1 affect antibacterial properties
Changes are R2 affect metabolism and pharmacokinetics
Mechanism of action of Cephalosporins
same as penicillins
Inhibit cell wall synthesis (act on transpeptidase/PBP)
Killing effect
Which Cephalosporin has the longest half life?
Ceftriaxone
Which cephalosporins cannot be used for meningitis? Why?
1st and 2nd generation
They don’t have good penetration into the CNS (except for Cefuroxime, but it doesnt treat the bugs that cause meningitis anyway)
Which Cephalosporins can treat Meningitis?
Some 3rd generations (Ceftriaxone, Ceftaxone, Ceftazidime)
Also Cefepime
Maybe Ceftaroline in the future
Cephalosporin metabolism/excretion
Excreted by the kidneys via the organic acid secretory system and by glomerular filtration.
Adjust dosage with renal failure
Ceftriaxone is different (excreted in bile)
Ceftriaxone excretion
Mainly excreted in the bile
No need to adjust for renal failure
Who shouldn’t get Cephalosporins?
Patients with a history of severe reactions to Penicillin family members
If their reaction to penicillins is very mild, you can cautiously try cephalosporins.
There is no skin test to predict allergic reactions to cephalosporins.
Adverse Effects of Cephalosporins
Alcohol intolerance, especially with Cefalozin (buildup of acetaldehyde because of aldehyde dehydrogenase inhibition)
Methythiotetrazole in the R2 position seen in Cefalozin is associated with particularly bad EtOH reaction
Bleeding disorders (kills off Vit K producing bacteria). Again, Cefalozin is especially bad here.
Also nephrotoxicity, seizures, GI problems, opportunistic infections.
How can you prevent bleeding disorders with Cephalosporin administration?
Vit K supplementation
Resistance Mechanisms to Cephalosporins
Beta lactamase (later generations are less and less susceptible to this) First generations are easily broken down by beta lactamase Cofaclor (2nd gen) is also susceptible.
What are 3rd gen Cephalosporins best at treating?
Gram Negatives
Strep pneumo
(Not good with most gram positives)
What are 2nd gen Cephalosporins best at treating?
Pretty equal at gram negative, strep pneumo, and gram positives
What are 1st gen Cephalosporins best at treating?
Strep pneumo
Gram positives
(Not good with Gram Negs)
First Gen Cephalosporin activity
Gram positives
Oral cavity anaerobes
Some gram negative enteric
Cefazolin
First gen cephalosporin
Drug of choice for surgical prophylaxis *** (probably on test)
Staph and strep infections in patients allergic to penicillins
Other minor infections
Not used for serious systemic infections
Second Generation Cephalosporin Activity
Gram positives (not as good as 1st gen)
Gram negatives like H flu, Moraxella (better than 1st gen)
Good for Upper respiratory infections because of this
Some anaerobic coverage
Cefoxitin has activity against Bacteroides fragilis and is used for mixed anaerobic infections
Never used for meningitis
Third Generation Cephalosporin Activity
More active against gram negatives than second generation
Less effective than first gen with gram positives
Useful against beta lactamase producing Neisseria and H flu
Wide use for many types of infections
Ceftazidime
3rd gen Cephalosporin
Active against Pseudomonas
Ceftriaxone and Cefotaxime
3rd gen Cephalosporins
Activity against penicillin-resistant Strep pneumo
First line therapy against Gonorrhea
Ceftriaxone followed by Cefixime (3rd generations)
Probably also use a macrolide or another antibiotic due to resistance.
Meningitis Cephalosporin Therapy
3rd Gen cephalosporins because they can cross BBB and have activity against meningitis agents
Ceftriaxone, Cefotaximi, Ceftaxidine
Add Ampicillin if you suspect Listeria
Lyme Disease Cephalosporin
Ceftriaxone treats neurological complications
Cefepime
4th gen cephalosporin
More resistant to beta-lactamases
Useful against Gram negatives that are resistant to 3rd gen
Useful against Enterobacter infections (UTI)
Active against penicillin-resistant Strep
Ceftaroline
5th gen cephaosporin
Activity against MRSA!!!***
Used for community acquired pneumonia and skin infections caused by Staph aureus/MRSA
