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PHRM 865: Theraputics V > Lecture 5: Penicillins > Flashcards

Lecture 5: Penicillins Flashcards

Cushman's Section

1
Q

What is important to know about Gram (+) Bacteria Structure?

A
  • Drugs penetrate easier
  • Increased B-lactamases
  • Thick cell wall
  • One Membrane
  • Bridge between L-Lys & D-Ala
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2
Q

What is important to know about Gram (-) Bacteria Structure?

A
  • Excludes Drugs [Has Porins Tho]
  • B-lactamases in Periplasmic Space
  • Thin cell wall
  • Two Membrane [Inner & Outer]
  • Bridge between DAP
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3
Q

Explain how Transpeptidase cross-links peptidoglycaon strands together?

A
  • Transpeptidase catalyzes peptidoglycan structure kicking off 1 D-Ala
  • Another peptidoglycan amino group binds to the other peptidoglycan structure
  • = Peptide-D-Ala-Gly-Gly-Peptide [Crosslinked]
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4
Q

What is the Mechanism of Action for the Penicillins?

A
  • Penicillins act like the Peptidoglycan Structure “fooling” the transpeptidase to bind to it inactiving it [NO CROSS-LINKS]
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5
Q

Why do Penicillins display selective toxicity for bacteria and NOT the host?

A
  • Bacteria contain D-Ala which is not found in host cells
  • Host has L-Ala
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6
Q

What are some of the ways that are Resistance to B-Lactams?

A
  • Decreased Uptake of Drug
  • Mutation of PBPs
  • Efflux Pumps [move drug out]
  • B-Lactamases [they will break the B-Lactam ring = inactived]
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7
Q

What is the meachanism of allergenicity of Penicillins?

A
  • B-lactam acts as Hapten [Pharmacophore of drug]
  • Allerigies to 1 B-lactam = probably ALL [could try Cephalos or Carbas]
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8
Q

What is the mechanism of Penicillin Degradation under Acidic and Basic conditions?

A
  • Ring breaks open??
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9
Q

In what way does lipophilicity of Penicillins affect serum protein binding?

A
  • Increases ClogP = Increases lipophilicity
  • More lipophilic side chains = more protein binding [decreases degradation]
  • Reducing bioavailability
  • Does not affect half-life
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10
Q

What are the Penicillin excretion mechanisms?

A
  • Excreted renally and biliary [90% Tubular & 10% Glomarular]
  • Half life longer in kidney disease
  • Penicillins are anioinic [so is probenecid] so increased half life

Nafcilin = Billiary

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11
Q

What is the way that Penicillins are distributed in the Body?

A
  • Basically everywhere except the CSF [if meningitis; use parenteral to enter CSF]
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12
Q

What is the way that Penicillins are synthesized?

A
  • Made by acykation of 6-APA
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13
Q

From Left to Right; what is the Nomenclature of the B-lactam ring system?

A
  • Penam
  • Penem
  • Carbapenem
  • Caphem
  • Monobactam
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14
Q

What are the characteristics of Penicillin G [Benzylpenicillin]?

Spectrum? B-lactamase Sens? Dosage? Toxicity? Precautions?

A
  • Spectrum: Gram (+) with N. Gonorrhoeae & H. Influenzae [resistance is common]
  • B-lactamase Sens: YES
  • Dosage: Oral or Parenteral [most effective]
  • Toxicity/Precautions: Allergic reaction –> use with cautions if so
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15
Q

What are the characteristics of Bicillin C-R [Bensylpenicillin Benzathine and Benzylpenicillin Procaine]?

Pharmacokinetics? Administration? Use?

A
  • PK: Low solubility = slow release from IM [Depo]
  • Administration: ONLY IM [IV = cardiac death & near nerve = neuro damage]
  • Use: Mod - Severe URTi, Scarlet Fever, Skin/Soft Tissue infections…
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16
Q

What is the main difference between Penicillin V and Penicillin G?

Chemical Feature?

A
  • PenV is more stable in acid; ether Oxygen decreasing nucleophilicity of the amide carbonyl side chain
17
Q

What are the major B-lactamase Resistant Parenteral Penicillins?

Anti-staph?

A
  • Methicillin
  • Nafcillin
  • Oxacillin
18
Q

What are the major B-lactamase Resistant Oral Penicillins?

Anti-staph

A
  • Oxacillin [D/C’d]
  • Clozacillin [D/C’d]
  • Dicloxacillin
19
Q

What are the B-lactamase Sensitive Broad Spectrum Oral Penicillins?

Amino?

A
  • Ampicillin
  • Amoxicillin
20
Q

What are the B-lactamase Broad Spectrum Parenteral Penicillins?

ureido?

A
  • Azlocillin
  • Mezlocillin
  • Piperacillin
21
Q

What is the way that Methicillin confers resistance to hydrolysis by B-lactamases?

A
  • 2 Methoxyls ORTHO to the amide; stop nucleophilic attacks; increasing stablilty
22
Q

What is the way, chemically, that Methicillin is so unstable to hydrolysis under acidic conditions?

A
  • Electron donation toward the amide cabonyl oxygen by the o-methoxy group, making the amide conbonyl oxygen more nucleophilic
23
Q

What is the antibiotic spectrum for Methicillin?

A
  • NARROW
  • Was used to treat S. Aureus BUT MRSA was formed becase of PBP mutation [PBP2A]
24
Q

What is the characteristics of Nafcillin with respect to B-lactamase sensitivity and acid stability?

A
  • B-lactamase Sens: NO
  • Slightly more stable than methicallin in acid because of big ring [clinically identicial tho]
25
Q

What is the structural similarites between Oxacillin, Cloxicillin, and Dicloxacillin?

A
  • Oxacillin: Ring only
  • Cloxacillin: Cl on ring
  • Dicloxacilin: 2 Cl on Ring
26
Q

What are the charatcteristics of the B-lactamase Resistant Oral Penicillins?

B-lactamase Sens? Spectrum? Protein Binding? Cross-Restantance?

A
  • ALL isoxazoles
  • B-lactamase Sens: NO
  • Spectrum: Less potent against Gram (+) that make B-lactam; good to those that do
  • Protein Binding: Highly = Not good in septicemia
  • Cross Resistant with Methicillin
27
Q

What is the bacterial spectrum of Ampicillin?

A
  • Gram (-) sensitive now; Salmonella, Shegella, P. Mirabilis, E. Coli, H. Influzenae, N. Gonorrhoeae
  • NH2 helps get through the porins better
28
Q

What is the reason that Ampicillin is stable in acid?

A
  • Amino Group is protonated in the stomach = N+ more attracting [decreases nuleophilicity so ring dont open]
29
Q

What is the main difference between Amoxicillin and Ampicillin with regards to Absroption?

A
  • Amox is an analog of Amp; phenolic group was added to the ring = better oral absorption
30
Q

What are the B-lactamase inhibitors that are used?

A
  • Clavulanic Acid
  • Sulbactam
  • Tazobactam
  • Avibactam
31
Q

How do the B-lactamase inhibitors work mechanistically?

A
  • Used in combo with the B-lactamase Sensitive Penicillins
  • Acylate the serine hydroxyl group on B-lactamase [inhibit B-lactamase & increase penicillin stablity]
32
Q

What are the products that use B-lactamase inhibitors?

A
  • Amoxicillin + Clavulante = Augmentin
  • Ampicillin + Sulbactam = Unasyn
  • Pipericillin + Tazobactam = Zosyn
  • Ceftrazidime + Avibactam = Avycaz
33
Q

Why do the Acylureidopenicillins have a broadened spectrum of antibacterial activity and enhanced potency?

A
  • Have a urea Moiety [increased activity to Gram (+) & Gram (-) (P. Aeruginosa, K. Pneumonia, B. Fragilis)
  • Enhanced Potenty because they added side chain fragments that look like peptidoglycan chains like Ampicillin

PHRM 865: Theraputics V (42 decks)

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