(3-22-17) Antibiotics Flashcards
who is most guilty for the emerging resistance of antibiotics?
agriculture
why are bacterioCIDAL drugs preferred to bacterioSTATIC?
- rely less on host immune system
- take effect more quickly
- maintain their effect longer, making exact dosing interval less critical
- very important for prophylaxis
***post antibiotic effects: seen with static drugs that may change its thinking
what is the post antibiotic defect?
persistent suppression of bacterial growth after a brief exposure (1-2 hrs) of bacteria to an antibiotic even in the absence of host defect mechanisms
*may be related to DNA alteration
which spectrum (narrow vs broad) is better and why?
NARROW
- often more effective
- less alteration of normal flora, therefore, less super infection
what is the dosage of a drug determined by?
- MIC minimum inhibitory conc
- -too much = toxicity
- -to littler = resistance
- -host function may alter
- -inc evidence that “loading dose” is helpful
what is the MIC?
minimum inhibitory conc
-minimum conc of a drug that will prevent visible growth of bacteria in culture after an overnight incubation
is rebound of infection common in oral/facial infection of odontogenic infection?
no
what is the general rule of thumb for termination of antibiotic?
when sure pt is on the way to recover based on clinical eval.
what are the 3 adverse effects of antibiotics?
- toxicity
- allergy
- superinfection
what are some examples of toxicity for antibiotics?
- GI distress
- hepatotoxicity (antifungals)
- nephrotoxicity (penicillin, aminoglycosides)
- neurotoxicity (aminoglycosides)
- blood and blood forming organs (choramphenicol, destruciton of normal flora needed for vit K absorption)
what are often confused with true allergies?
toxicities or side effects
*multiple allergies may severely limit critical therapy
in what circumstances are superinfections more common?
- young and old
- broad spectrum therapy
what do superinfections sometimes cause?
inc or dec in effectiveness of other drugs
ie birth control pills
what is pseudomembranous colitis?
- caused by C. difficile
- cephs, ampicillin, clindamycin
- frequent, watery/bloody diharrea and cramps
- stop drug immediately
- oral vancomycin is no longer accepted tx
- METRONIDAZOLE is now used to treat
what is an optimal antibiotic?
- active against pathogen
- reaches effective conc
- low toxicity
- not cause resistance
- desirable route
- economical
T/F oral bacteria are commonly primary pathogens?
FALSE
gererally several organisms not just one
*resistnace is no longer a “non-issue” as it has been in the past
widest spectrum of all antibacterials
beta lactam antibiotics
from narrow to broad range spec:
- PENICILLINS
- CEPHALOSPORINS
- carbapenems
- monobactams
- carbacephems
what is the mechanism of action of penicillins?
cell wall synthesis
- prevents cross linking
- low toxicity in general
Pen V
- combine with potassium or sodium to make a salt (Pen VK)
- stable in gastric pH (orally effective)
- low toxicity
- narrow spectrum specific to oral microbes
- CIDAL
- inexpensive
Pen G
- IV or IM only
- unstable in gastric contents
- formulated as: aqueous, procaine, benzathine
what is the drug of choice for most odontogenic infections?
Penicillin
what is the dosing rule for penicillin?
may load up to 2 grams followed by 500 mg every 6 hrs
*parenteral dosage given as “units”
in what circumstances should you dec dose for penicillin?
- renal compromised
- infants
B-lactamase resistant penicillins
- “anti-staph” penicillins
- methicillin was prototype (MRSA)
- less activity against oral bacteria
- expensive
- indicated for ONLY STAPH infections
Extended spectrum penicillins (Amoxicillin group)
amoxicillin is the one that is used orally
is amoxicillin B-lactamase resistant?
no
why is amox better for SBE prophylaxis than PCN VK?
- more predictable
- longer half life
- higher plasma conc
- is NOT USED bc it is broader spectrum
- *these properties along with better dosage regimen may make amox an acceptable alternative to PCN for odontogenic infections
Extended spectrum penicillins
anti-pseudomonas penicillins
- carbenicillin, ticarcillin, piperacillin, and others
- less activity against oral bacteria
- NOT INDICATED for any head and neck infection as DOC
beta lactamase
- cleave the B-lactam ring
- 100’s described
- transferred to bacteria by infective process
- combated by inc “R” chains or by competitive inhibition
beta-lactam inhibitors
3 available:
- clavulonic acid
- sulbactam
- tazobactam
*bind active site of B-lactamase action
Augmentin
- amox + clavulonic acid
- augmentin XR
- oral
- improved staph and H. flu coverage
what are the indications for augmentin?
- otitis (ear)
- bite wounds
- sinusitis (non-odontogenic)
- UTI
Unasyn
- ampicillin + sulbactam
- parenteral
- similar spectrum as augmentin
- due to inc resistance to PCN, it is the DOC for serious infections being treated in a HOSPITAL SETTING
what are the adverse effects of penicillins?
- allergy (1-10% occurence)(2% average)(usually not fatal)
- antagonized by bacteriostatic drugs
- dec excretion in very young, old, or compromised renal function
most frequent DOC for odontogenic infection
PCN V
DOC for hospital infection
unasyn
if significant anerobic component of infection, what is the DOC?
metronidazole
DOC for bites, non-odontogenic sinusitis, otitis?
B-lactamase inhibitiors such as augmentin
DOC for prophylaxis?
amox
cephalosporins
- 5 generations
- beta-lactam configurations
- inc resistnace to B-lactamase by addition of R groups
- “custom” antibiotics
cephalosporin pharmacology
- cidal- cell wall inhibition
- low toxicity
- extended spectrum in comparison to PCN
- oral and parenteral forms
- expensive in comparison to PCN
first generation ceph
-parenteral
steph, staph, e coli, MSSA not MRSA
second generation ceph
-oral
what are the indications for a first generation cephalosporin
- community aquired staph infection
- surgical wound prophylaxis with skin incision
- odontogenic infection in pen allelrgic pt
what is the incidence of a PCN allergy?
5-8%
what % of PCN allergics will have ceph allergy as well?
1-10%
*ceph allergy predisposes to unknown incidence of PCN allergy
if pt has severe PCN allergy, should you avoid ceph?
yes, if severe
*should be fine if the allergy is mild
if pt has ceph allergy, should you avoid PCN?
yes ALWAYS, even if it is mild
what is the mechanism of action for macrolides
- irreversibly bind 50s ribosomal units
- inhibit RNA dependent protein synthesis
- selective uptake by phagocytic cells which serve as repository. leads to high levels at infection relative to blood levels
- significant post-antibiotic effect
clarithromycin
- similar to erythromycin
- less resistance
- better H. influenza coverage
- BID dosing (250mg)
- less GI distress
- 1 hr before or 2 hr after eating
- expensive
what are the indications for clarithromycin?
- sinus infection
- Mild to moderate odontogenic infection in PCN allergic pt
- SBE prophylaxis in PCN allergic pt as alternate to clindamycin
- pneumonia/ bronchitis
azithromycin
- similar to clairithromycin but better for strep and g- anerobes
- 3 day course as effective as 7-10 days of augmentin
- pneumonia/ bronchitis
- SBE prophylaxis
- daily dosing/ improved compliance
- not require dosing around meals
- less GI distress
- expensive
what are the adverse effects of macrolides?
- GI distress, worse with erythromycin
- ototoxicity
- cholestatic jaundice
- long Q-T interval/Torsades de pointes
- inc activity of digitalis
- potentiation of oral anticoagulants such as coumadin
- myopathy in pts taking statins for elevated cholesterol
lincosamides
- bind 50s ribosome leading to bacteriostatic inhibition of protein synthesis
- clindamycin- currently the only one in use in US
what is the spectrum of clindamycin?
- strep
- staph
- actinomyces
- anaerobes
what is the pharmacology of clindamycin?
- static except at high doses
- bone penetration
- higher toxicity than some
- expensive
what are the indications of clindamycin?
- chronic recurrent infection
- osetomyelitis
- odontogenic infection in immunocompromised pt with severe PCN allergy
- inc use in routine odontogenic infection due to inc resistance to PCN by oral anearobes
metronidazole
- CIDAL
- oral dose equivalent to parenteral
- mild toxicity
- disulfuram effect
- inexpensive
- disrupts DNA in anaerobic environment
what are the indications for metronidazole?
- chronic anaerobic infection
- any need for bone penetration
- in combo with PCN or ceph in serious odontogenic infection
tetracyclines
- static - 30s ribosomal inhibition
- broad spectrum
- high resistance
- inexpensive
what are the indications for tetracyclines?
- early adjunctive tx of peri-implantitis
- resistant hospital aquired infections
- helobactor related gastric and peptic ulcer due to inc resistance to metronidazole
- topical therapy
- dry socket prevention
- NO INDICATION FOR ODONTOGENIC INFECTION
- may result in deformity of developing teeth
