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Clinical Pharmacology > Penicillins > Flashcards

Penicillins Flashcards

1
Q

Extended spectrum Penicillins

A
  • Amoxicillin
  • Ampicillin
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2
Q

Extended spectrum penicillins + beta-lactamase inhibitors

A

Amoxicillin + Clavulanic Acid (Augmentin)

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3
Q

Anti-staphylococcal (beta-lactamase resistant) Penicillins

A
  • Dicloxacillin
  • Cloxacillin (not approved in the US)
  • Methicillin, Oxacillin
    • ​IV use ONLY
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4
Q

What are the 4 major beta-lactam antibiotic families?

A
  1. Penicillins
  2. Cephalosporins
  3. Monobactams
  4. Carbapenems
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5
Q

What is the spectrum of activity of Penicillin?

A
  • Gram (+) cocci and rods
  • Most oral anaerobes
  • Treponema pallidum and some other spirochetes
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6
Q

What is the MOA of Bactericidal Penicillin?

A
  • 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
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7
Q

What is the MOA of Bacteriostatic Penicillin?

A
  • 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
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8
Q

How is penicillin V metabolized and excreted?

A

90 - 100% is excreted by kidneys unchanged

* One of the only ones!

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9
Q

What is the usual adult oral dose for penicillin?

A

(Tablets) 1 - 2 grams stat, then 500 mg, every 6 hrs

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10
Q

What does amoxicillin have better activity against than penicillin V?

A

Gram (-) bacteria

More active against enterococci

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11
Q

What has amoxicillin been shown to be active against in vitro?

A

Aggregatibacter actinomycetemcomitans

perio bacteria

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12
Q

What is the route of metabolism and excretion for amoxicillin?

A
  • Metab partially in the liver
  • Excreted 60% unchanged by kidneys
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13
Q

What is the usual adult oral dose for the tx of orofacial infections for amoxicillin?

A

500 mg every 8 hrs

OR

875 mg every 12 hrs

No loading dose needed

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14
Q

What drug(s) are used in the tx of perio infections such as NUG?

A

amoxicillin or penicillin V

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15
Q

What is the 1st choice drug (and dose) used for antibiotic prophylaxis for the prevention of metastatic infections (bacterial endocarditis) in non-allergic pts?

A

Amoxicillin 2 grams, 30 - 60 mins prior to dental tx

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16
Q

What are some potential adverse side effects of amoxicillin?

A
  • Greater potential to produce superinfection of the vagina and GI tract (including C. difficile diarrhea)
  • Non-allergic pruritic skin rash“ampicillin/amoxicillin rash”
17
Q

What is the most common mechanism of resistance to beta-lactam antibiotics?

A

Enzymatic inactivation: hydrolysis by beta-lactamase enzymes

18
Q

What 2 large groups are the most noticeable penicillin-resistant bacteria involved in odontogenic infections?

A
  • Viridans group streptococci
    • ​due to modifications in PBP
  • Strict anaerobic gram (-) rods = porphyromonas, prevotella, fusobacterium species
    • due to increasing beta-lactamase synthesis capacity
19
Q

If within 48 hrs the pt is not responding to penicillin or amoxicillin, what could you consider?

A
  • 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
20
Q

What is metronidazole’s unique MOA?

A

penetrating all bacterial cells and inhibiting DNA replication

21
Q

MOA of Augmentin

A

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)

22
Q

Staphylococci which are resistant to methicillin and/or oxacillin must be considered resistant to what?

A

Augmentin

Will not work on MRSA!!!

23
Q

What is the usual adult oral dose for the tx of orofacial infections with Augmentin?

A

1000/250 mg stat, then 500/125 mg, every 8 hrs

= Amoxicillin/claculanate potassium

24
Q

What are the indications for use of Augmentin in dentistry?

A
  • 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
25
Q

What is the primary indication for use of Dicloxacillin?

A

Tx of infections caused by penicillinase-producing staphylococci (S. aureus)

1 g stat then 500mg every 6 hrs

26
Q

Pts with IgE mediated allergic rxns to penicillins will frequently be allergic to what else?

A
  • Carbapenems (imipenem
  • 1st generation cephalosporins

Can generally tolerate 2nd - 4th gen cephalosporins and monobactams (aztreonam)

27
Q

Oral penicillins (penicillin V, amoxicillin) may be antagonized by what other drugs?

A

Bacteriostatic antibiotics

  • Tetracycline
  • Erythomycin
  • Clindamycin
28
Q

What drugs increase the serum half-lives of penicillins by decreasing their renal excretion?

A
  • NSAIDs
  • Probenecid
29
Q

Ampicillin or amoxicillin, when taken with what drug, can be associated with a nonurticarial rash?

A

Allopurinol

Clinical Pharmacology (9 decks)

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