Penicillins - SOA Flashcards
What are the six general characteristics of the B-lactams abx?
- Same mechanism of action
- Same mechanisms of resistance
- same pharmacodynamic properties
- short elimination half-life (<2 hours)
- renal elimination
- cross-allergenicity
Which abx classes are B-lactams?
- penicillins
- cephalosporins
- carbapenems
- monobactams
What is the general mechanism of action for the B-lactams?
Inhibit cell wall synthesis
What are the mechanisms of resistance to B-lactams?
pcns, cephalosporins, carbapenems
- destruction by B-lactamase enzymes
- alteration in PBPs
- decreased permeability of outer cell membrane in gram-negative bacteria
PBP = penecillin binding protein
What pharmacodynamic properties do the B-lactams display?
- B-lactams display time-dependent bactericidal activity
- T>MIC
Which species do B-lactams not display time-dependent bactericidal activity against?
- enterococcus spp
- they are bacteriostatic against enterococcus
Which B-lactams do not have a short half-life?
- ceftriaxone (3rd gen)
- cefotetan (2nd gen)
- cefixime (3rd gen)
- ertapenem
What is the half-life of ceftriaxone?
third-gen cephalosporin
8 hours
Which B-lactams are not renally eliminated?
- nafcillin
- oxacillin
- ceftriaxone
- cefoperazone
Which B-lactam does not display cross-allergenicity?
- aztreonam (monobactam)
Aztreonam can be used in patient with anaphylaxis to PCNs
Why is the production of B-lacatamase enzyme a more efficient mechanism of resistance in gram-negative bacteria?
- B-lactamase enzymes produced by GN bacteria reside in the periplasmic space – which makes them more concentrated
List the natural penicillins:
- aqueous pen G
- benzathine pen G
- procaine pen G
- pen VK
Which orgnaisms does penicillin G have activity against?
- enterococcus (GP)
- neisseria (GN)
These are not target organisms
What is the general SOA of penicillin G?
Natural PCN
- covers GP aerobes
- very limited GN
- covers ADA
What is the drug of choice for syphillis (treponema pallidum)?
natural penecillins (pen VK)
List the penicillinase-resistant penicillins (anti-staphylococcal pcns):
- nafcillin
- methicillin
- dicloxacillin
Which target organisms does nafcillin have activity against?
penicillinase-resistant penicillin
- MSSA (methicillin susceptible staph aureus
What is the general SOA of nafcillin?
penicillinase-resistant pcn
- gram positive aerobes (MSSA)
- nothing else
List the aminopenicillins:
- ampicillin
- amoxicillin
Why were the aminopenicillins developed?
Aminopcns were developed to address the need for pcns with extended activity against GN aerobic bacilli.
What is the general SOA of ampicillin?
aminopenicillin
- covers GP aerobes
- covers GN aerobes
- covers ADA
They don’t do a good job against GN anymore
When would aminopenicillins be the drug of choice?
ampicillin, amoxicillin
Aminopenicillins are the DOC for infections due to listeria monocytogenes and enterococcus spp.
List the carboxypenicillins:
ticarcillin
Developed to address the emergence of more resistant GN bacteria and the increasing frequency of pseudomonas aeruginosa
Which target organisms do carboxypenicillins cover?
ticarcillin
- pseudomonas aeruginosa
What is the general SOA of ticarcillin?
carboxypenicillin
- GN aerobes
nothing else
List the ureidopenicillin:
piperacillin
What is the general SOA of piperacillin?
ureidopenicillin
- GP aerobes
- GN aerobes
- ADA
- BDA
Which target organisms does piperacillin have activity against?
ureidopenicillin
- pseudomonas aeruginosa
- BDA
Which penicillin is the most active against pseudomonas aeruginosa?
piperacillin
List the B-lactamase inhibitor combinations:
- amoxicillin/clavulanic acid - PO
- ampicillin/sulbactam - IV
- piperacillin/tazobactam - IV
- Augmentin
- Unasyn
- Zosyn
What is the benefit of the B-lactamase inhibitor combo pcns?
They have enhanced activity against some B-lactamase producing bacteria such as MSSA and BDA
When can penicillins get into the CSF?
PCNs are widely distributed
Adequate concentrations of pcns in the CSF are attainable only in the presence of inflamed meninges when high, maximal doses of parenteral pcns are used.
Which pcn are note eliminated by the kidneys?
- nafcillin
- oxacillin
Nafcillin and oxacillin are eliminated primarily by the liver.
Piperacillin undergoes dual elimination .
Which pcns have a high sodium load?
- aqueous sodium pen G
- nafcillin
- ticarcillin
- piperacillin
ticarcillin has the highest (5.2 mEq per gram)
In which patients do we need to be mindful of the sodium load of certain parenteral pcns?
PenG, nafcillin, ticarcillin, piperacillin
- Congestive heart failure
- renal dysfunction
What infections are penicillinase-resistant pcns useful for?
nafcillin, oxacillin
Due to their enhanced activity against staph aureus, nafcillin and oxacillin are useful in the treatment of infections due to MSSA.
When do neurologic adverse effects occur when using pcns?
Direct toxic effects are observed primarily in patients who receive large IV doses of renally-eliminated pcns in the presence of renal dysfunction.
What is amox-clav (Augmentin) good for?
human or animal bites
What are the adverse effects of concern for penicillins?
- interstitial nephritis
- reversible leukopenia, neutropenia, thrombocytopenia
- GI
- neurologic toxicity
- hypersensitivity reactions
- phlebitis
- hypokalemia
Which penicillins are associated with interstitial nephritis?
- methicillin
- nafcillin
Can occur in others, but these are most common.
What are the manifestations of interstitial nephritis?
- fever
- eosinophiluria
- abrupt increase in Scr
