Penicillins Flashcards
Extended spectrum Penicillins
- Amoxicillin
- Ampicillin
Extended spectrum penicillins + beta-lactamase inhibitors
Amoxicillin + Clavulanic Acid (Augmentin)
Anti-staphylococcal (beta-lactamase resistant) Penicillins
- Dicloxacillin
- Cloxacillin (not approved in the US)
-
Methicillin, Oxacillin
- IV use ONLY
What are the 4 major beta-lactam antibiotic families?
- Penicillins
- Cephalosporins
- Monobactams
- Carbapenems
What is the spectrum of activity of Penicillin?
- Gram (+) cocci and rods
- Most oral anaerobes
- Treponema pallidum and some other spirochetes
What is the MOA of Bactericidal Penicillin?
- Kill bacterial cells only when they are actively growing and synthesizing a cell wall via osmotic rupture of bacteria due to ongoing activity of cell wall autolytic enzymes while cell wall assembly is arrested
What is the MOA of Bacteriostatic Penicillin?
- Via inhibition of bacterial cell wall synthesis by binding one or more of the penicillin-binding proteins (PBPs)
- Which in turn inhibits the final transpeptidation rxn of peptidoglycan synthesis in bacterial cell walls, thus inhibiting cell wall biosynthesis
How is penicillin V metabolized and excreted?
90 - 100% is excreted by kidneys unchanged
* One of the only ones!
What is the usual adult oral dose for penicillin?
(Tablets) 1 - 2 grams stat, then 500 mg, every 6 hrs
What does amoxicillin have better activity against than penicillin V?
Gram (-) bacteria
More active against enterococci
What has amoxicillin been shown to be active against in vitro?
Aggregatibacter actinomycetemcomitans
perio bacteria
What is the route of metabolism and excretion for amoxicillin?
- Metab partially in the liver
- Excreted 60% unchanged by kidneys
What is the usual adult oral dose for the tx of orofacial infections for amoxicillin?
500 mg every 8 hrs
OR
875 mg every 12 hrs
No loading dose needed
What drug(s) are used in the tx of perio infections such as NUG?
amoxicillin or penicillin V
What is the 1st choice drug (and dose) used for antibiotic prophylaxis for the prevention of metastatic infections (bacterial endocarditis) in non-allergic pts?
Amoxicillin 2 grams, 30 - 60 mins prior to dental tx
What are some potential adverse side effects of amoxicillin?
- Greater potential to produce superinfection of the vagina and GI tract (including C. difficile diarrhea)
- Non-allergic pruritic skin rash“ampicillin/amoxicillin rash”
What is the most common mechanism of resistance to beta-lactam antibiotics?
Enzymatic inactivation: hydrolysis by beta-lactamase enzymes
What 2 large groups are the most noticeable penicillin-resistant bacteria involved in odontogenic infections?
-
Viridans group streptococci
- due to modifications in PBP
- Strict anaerobic gram (-) rods = porphyromonas, prevotella, fusobacterium species
- due to increasing beta-lactamase synthesis capacity
If within 48 hrs the pt is not responding to penicillin or amoxicillin, what could you consider?
- Adding metronidazole 500 mg every 6-8 hrs, for the duration of tx
- Only active against obligate anaerobes
- Switiching to amoxicillin + clavulanic acid (Augmentin)
- Switching to clindamycin
- Switiching to Group II fluoroquinolone (ciprofloxacin)
- Switching to diclozacillin (?)
- Last resort
What is metronidazole’s unique MOA?
penetrating all bacterial cells and inhibiting DNA replication
MOA of Augmentin
Clavulanic acid has no antibacterial activity itself but possesses the ability to inactivate a wide varity of beta-lactamases (prevent their hydrolysis of beta-lactam antibiotics)
Staphylococci which are resistant to methicillin and/or oxacillin must be considered resistant to what?
Augmentin
Will not work on MRSA!!!
What is the usual adult oral dose for the tx of orofacial infections with Augmentin?
1000/250 mg stat, then 500/125 mg, every 8 hrs
= Amoxicillin/claculanate potassium
What are the indications for use of Augmentin in dentistry?
- Orofacial infections caused by B-lactamase producing bacteria (staphylococci) when a bacterial culture and sensitivity tests
- and/or that are unresponsive to penicillin V or amoxicillin
- Adjunctive tx of rapidly progressive periodontitis
