Contemporary Antibiotics Flashcards
why should you start with empiric therapy instead of definitive therapy for odontogenic infections?
b/c fairly predictable for odontogenic infections and inadequate time for cultures to grow
what is bacteriCIDAL more preferable than bacterioSTATIC abx?
cidal drugs…
- rely less on host immune system
- take effect more quickly
- maintain their effect longer, making exact dosing interval less critical
- very important for prophylaxis since the goal is to destroy all bacteria
post antibiotic effect (PAE)
persistent suppression of bacterial growth after a brief exposure (1 or 2 hours) of bacteria to an abx even in the absence of host defense mechanisms
what may be related to post antibiotic effect (PAE)?
DNA alteration
why is a narrow spectrum abx better?
- often more effective
2. less alteration of normal flora so less super infection
examples of narrow spectrum abx
- penicillin VK
2. penicillin G +metronidazole
examples of broad spectrum abx
- amoxicillin
- cephalexin
- unasyn
dosage of abx are determined by what?
minimum inhibitory concentration (MIC)
what happens if abx dosage is too high?
toxicity
what happens if abx dosage is too low?
resistence
T/F: there has been increasing evidence that “loading dose” is helpful (2-4x’s therapeutic dose)
true
how is minimum inhibitory concentration (MIC) measured?
in vitro
T/F: minimum inhibitory concentration (MIC) only serves as a guide to abx dosing therapy since we cannot tell what concentration is at infection
true
what is minimum inhibitory concentration (MIC)?
minimum concentration of a drug that will prevent visible growth of bacteria in culture after an overnight incubation
T/F: rebound of infection is common in oral/facial infection of odontogenic origin
false, rare
what is the general rule of thumb when it comes to duration of abx?
terminate abx when sure patient is on the way to recover based on clinical evaluation
adverse effects of abx
- toxicity
- allergy
- super infection
which drugs in particular causes hepatotoxicity?
antifungals
which drugs causes nephrotoxicity?
- penicillin
2. aminoglycosides
which drugs causes neurotoxicity?
aminoglycosides
which drug causes blood and blood forming organs?
chloramphenicol
how does chloramphenicol cause blood and blood forming organs?
destruction of normal flora needed for vitamin K absorption
what does an allergy serve as?
haptans binding with host protein
which category of drugs are more prone to allergies?
penicillin
what percent of the population has a cross-allergy to penicillin and cephalosporin?
10-15%
what is often confused with true allergy?
toxicity or side effect
superinfection is more common with what?
broad spectrum therapy
examples of superinfection?
- pseudomembranous colitis (Clostridium difficile)
2. candida
what can increase or decrease effectiveness of abx?
birth control pills
which abx may cause pseudomembranous colitis (Clostridium difficile)?
- cephalosporins
- ampicillin
- clindamycin
what is no longer used to treat pseudomembranous colitis (Clostridium difficile)?
oral vancomycin
what is now used to treat pseudomembranous colitis (Clostridium difficile)?
metronidazole
what makes an optimal abx?
- active against pathogen
- reaches effective concentration
- low toxicity
- not cause resistence
- desirable route
- economical
T/F: oral bacteria are rarely primary pathogens causing orofacial infection
true, there are several organisms not just one
beta-lactam abx
- penicillins
- cephalosporins
- carbapenems
- monobactams
- carbacephems
what is the widest spectrum of activity of all antibacterials?
beta-lactam antibiotics
which are natural penicillins?
PCN V and G
which are B-lactamase resistant penicillins?
- oxacillin
2. dicloxacillin
which are extended spectrum penicillins?
- amoxicillin group (i.e. ampicillin)
2. anti-pseudomonas group (i.e carbenicillin)
which are extended spectrum PCN with B-lactamase inhibitors?
- Augmentin
2. Unasyn
mechanism of action of penicillins
cell wall synthesis disruption by preventing cross linking
penicillin V is a combination of what?
potassium or sodium to make a salt
what is the most common penicillin V?
PCN VK
pros of penicillin V
- stable in gastric pH so orally effective
- low toxicity
- narrow spectrum specific to oral microbes
- cidal
- inexpensive
T/F: penicillin V has less activity against gram negative bacilli than extended spectrum penicillins
true
how is penicillin G administrated?
IV or IM only since unstable in gastric contents
what is the drug of choice for most odontogenic infections?
penicillion
dosage of penicillin
may load with up to 2 grams followed by 500mg every 6 hours
dosage of penicillin may need to be decreased in who?
patients with renal compromise and infants
B-lactamase resistant penicillins are also known as what?
“anti-staph” penicillins
which B-lactamase resistant penicillin is the prototype?
methicillin hence term “methicillin resistant staph” or MRSA
how is oxacillin given?
parenteral
how is dicloxacillin given?
oral
cons of B-lactamase resistant penicillins
- less activity against oral bacteria
2. expensive
when are B-lactamase resistant penicillins indicated?
for proven staphylococcal infections
how is ampicillin given?
parenteral
how is amoxicillin given?
oral
extended spectrum penicillins (amoxicillin group) are given for which type of bacteria?
- streptococcus
- oral anaerobes
- H. influenza
- E. coli
- salmonella
- shigella
- proteus
when is amoxicillin indicated?
- otitis media
- UTI
- SBE prophylaxis
- maybe for odontogenic infection if culture and specifity indicates use
T/F: amoxicillin is B-lactamase resistant
false, is NOT
why is amoxicillin given for SBE prophylaxis instead of PCN VK?
- more predictable absorption
- longer half life
- higher plasma concentration than PCN VK
- PCN VK not used because of broader spectrum
dosage regimen for amoxicillin and SBE prophylaxis
500 mg q 8h
examples of extended spectrum penicillins (anti-pseudomonas penicillins)
- carbenicillin
- ticarcillin
- piperacillin
T/F: extended spectrum penicillins (anti-pseudomonas penicillins) are effective against oral bacteria
false
when is extended spectrum penicillins (anti-pseudomonas penicillins) not indicated?
for any head and neck infection as DOC
B-lactamase fxn
enzyme that cleaves B-lactam ring
how is B-lactamase combated?
by increasing “R” chains or by competitive inhibition
B-lactam inhibitors currently available
- clavulonic acid
- sulbactam
- tazobactam
mechanism of action of B-lactam inhibitors
bind to active site of B-lactamase
augmentin
amoxicillin + clavulonic acid
how is augmentin given?
oral
augmentin improved coverage of what?
staph and H. flu
indications for augmentin
- otitis
- bite wounds
- sinusitis (non-odontogenic)
- UTI
unasyn
ampicillin + sulbactam
how is unasyn given?
parenteral
T/F: unasyn has a similar spectrum as augmentin
true
due to increasing resistance to PCN G, what is now the DOC (drug of choice) for serious infections being treated in a hospital setting
unasyn
adverse effects of penicillins are antagonized by what?
bacteriostatic drugs
adverse effect of penicillin in very young, old or compromised renal fxn
decreased excretion
what is the most frequent drug of choice for odontogenic infection?
PCN V
what is a suitable alternative to PCN VK?
amoxicillin
why is amoxicillin a suitable alternative to PCN VK?
better absorption and blood levels and dosing regimen
if patient has a significant anaerobic component, which abx may be indicated?
metronidazole
bites, non-odontogenic sinusitis, otitis require what?
B-lactamase inhibitors such as in augmentin
