Ab Flashcards
(65 cards)
Cell Wall Synthesis Inhibitors
β-lactam drugs: Penicillins, Cephalosporins, Carbapenems, Monobactams
Beta-lactamase inhibitors: NOT antibiotics but are used in a combination with extended-spectrum PCN
Non-β-lactam drugs
All bactericidal since cell lyses without wall.
Classical PCNs
gram (+), bactericidal, relatively narrow spectrum (mostly active against Gram-positive such as Staphylococcus) Penicillin G (IV) Penicillin V (oral) Procaine penicillin G (IM) Benzathine penicillin G (IM)
b-lactamase-resistant (anti-Staphyloccocal)
PCNs
gram (+), b-lactamase resistant (resistant to hydrolysis by beta-lactamase (penicilinase) found in many Staphylococcus aureus), bactericidal,
- -bacteria sensitive to this class of PCNs are called methicillin-sensitive SA (MSSA).
- -bacteria that are resistant to this class of PCNs are called methicillin-resistant SA (MRSA)
Methicillin (Don’t use since toxic to kidney-nephritis) Nafcillin Oxacillin Cloxacillin Dicloxacillin
Extended-Spectrum
PCNs
gram (+) and (-), bactericidal, more active against gram-negative bacteria compared to penicillin G/V
AMINOpenicillins: AMipicillin, AMoxicillin
Anti-pseudomonal PCNs:
CARBOXYpenicillins: CARbenicillin, TiCARcillin
UREIDOpenicillins: Piperacillin, Mezlocillin
-often used in a combination with beta-lactamase inhibitors to treat infections caused by Pseudomonas aeruginosa
Cephalosporins
gram (+): 1st gen gram (-): 2nd, 3rd b-lactamase resistant: 3rd/4th/5th broad spectrum: 4th, 5th bactericidal
Carbapenems
gram (+), gram (-), b-lactamase resistant, broad spectrum, bactericidal
Monobactams
gram (-), bactericidal, only aztreonam
Non-b-lactams
gram (+), bactericidal
Penicillins structure and MOA
D-Ala-D-Ala analogs, belong to beta-Lactams
MOA: Bind to PBP, inhibit transpeptidation
three sub groups of drugs that are of different antibacterial spectrum
Pros and Cons of Classical PCNs
penicillin G, penicillin V
pros: Active against G(+), some G(-) cocci and anaerobes
cons: Inactive against G(-) rods; hydrolyzed by β-lactamase
- -narrow spectrum and are often used to treat infections caused by gram-positive bacteria such as Staphylococcus aureus
- -penicillin G remains the drug of choice for treating syphilis which is caused by a spirochete
Pros and Cons of b-lactamase resistant PCNs (Anti-Staphylococcal PCN)
methicillin, nafcillin, cloxacillin, dicloxacillin
- -not broad spec. just good for beta lactam resistant bugs
- -even narrower spectrum than classical PCNs
pros: Resistant to Staphylococcal β-lactamase
cons: Inactive against G(-), anaerobes, enterococci
Pros and Cons of Extended-spectrum PCNs
ampicillin, amoxicillin, carbenicillin, ticarcillin, piperacillin, mezlocillin
pros: Improved activity against G(-) organisms
cons: Hydrolyzed by β-lactamase
- -can be used in fixed combinations with beta-lactamase inhibitors to broaden their antibacterial spectrum
Cephalosporins and Cephamycin
Structure: D-Ala-D-Ala analogs, belong to beta-Lactams
MOA: Bind to PBP, inhibit transpeptidation
Same MOA and major side effects as all beta-lactams
-Different spectrums
-Cross-allergenicity with PCN
-Most are renally cleared
-Many 3rd generation cephalosporins are also more likely to cross BBB to reach CNS and are thus useful for treating CNS infections.
-4th and 5th aren’t called broad spectrum since it kills many positive and negatives but not all.
-Covers even anaerobes.
-5th generation ceftobiprol is active against MRSA
1st generation Cephalosporins
Cefazolin (Inj.)
Cephalexin
Cephalothin
Cephradine
–more active against G(+), but less effective against most G(-)
Structure: D-Ala-D-Ala analogs belong to beta-Lactams
MOA: Bind to PBP, inhibit transpeptidation
Same MOA as all beta-lactams
Different spectrums
Cross-allergenicity
Most are renally cleared
2nd generation Cephalosporins and Cephamycin*
Cefaclor Cefprozil Loracarbef Cefuroxime Cefoxitin* Cefotetan* Cefonicid
–more active against G(-), but less active against G(+) compared to 1st generation
Structure: D-Ala-D-Ala analogs belong to beta-Lactams
MOA: Bind to PBP, inhibit transpeptidation
Same MOA as all beta-lactams
Different spectrums
Cross-allergenicity
Most are renally cleared
3rd generation Cephalosporins
Cefoperazone Cefotaxime Ceftazidime Ceftizoxime Ceftriaxone Cefixime Cefpodoxime Cefdiner Cefibuten --more active against G(-), but less effective against most G(+) --Many are also more likely to cross BBB to reach CNS and are thus useful for treating CNS infections. Structure: D-Ala-D-Ala analogs belong to beta-Lactams MOA: Bind to PBP, inhibit transpeptidation Same MOA as all beta-lactams Different spectrums Cross-allergenicity Most are renally cleared
4th generation Cephalosporins
cefepime most active against both G(+) and G(-) Structure: D-Ala-D-Ala analogs belong to beta-Lactams MOA: Bind to PBP, inhibit transpeptidation Same MOA as all beta-lactams Different spectrums Cross-allergenicity Most are renally cleared
5th generation Cephalosporins
Ceftaroline
Structure: D-Ala-D-Ala analogs belong to beta-Lactams
MOA: Bind to PBP, inhibit transpeptidation
Same MOA as all beta-lactams
Different spectrums
Cross-allergenicity
Most are renally cleared
Other b-lactams: Carbapenems
Imipenem*
Ertapenem
Meropenem
Structure: D-Ala-D-Ala analogs belong to beta-Lactams
MOA: Bind to PBP, inhibit transpeptidation
–broad-spectrum beta-lactams that are useful for treating mixed infections
*Imipenem + cilastatin (inhibits renal dehydropeptidase: prolongs imipenem’s bioavailability)
Imipenem inhibited by dehydropeptidase
Other b-lactams: Monobactams
Aztreonam
Structure: D-Ala-D-Ala analogs belong to beta-Lactams
MOA: Bind to PBP, inhibit transpeptidation
–is active against gram-negative only
–does not share drug resistance with PCNs and is therefore useful for treating PCN-resistant infections.
Other b-lactams: β-lactamase inhibitors*
Clavulanic acid
Sulbactam
Tazobactam
- -Little/no antibiotic activity: are beta-lactams but are NOT antibiotics
- -MOA: inh. b-lactamase)
- -Used only in fixed combination with specific extended-spectrum penicillins to broaden their antibacterial activity
Non-b-lactam Cell Wall Syn. Inh. - Fosfomycin
Spectrum/Use: G(+), G(-) MOA: Inh. enolpyruvate transferase --blocks NAM --"F" for first step --good for uti when other drugs don’t work
Non-b-lactam Cell Wall Syn. Inh. - Cycloserine
Spectrum/Use: TB
MOA: Inh. alanine racemase, blocks synthesis of linking pentapeptide (PEP)
Non-b-lactam Cell Wall Syn. Inh. - Vancomycin
Spectrum/Use: G(+)
MOA: Binds to D-Ala-D-Ala
–not orally absorbed since it is a glycopeptide
–doesn’t get in through gut easily since it is charged
–so not orally bioavailable
–used in general as injection/infusion except for C. diff colitis (overgrowth from too much ab)
