Abx 2 (inhibitors of cell wall synthesis)

Question 1

Penicillin G (Benzathine)

Answer 1

• Beta Lactam
• Standard narrow spectrum
• G+
• Parenteral
• DOC for syphilis
• Repository prep- 1 IM dose producing persistent but low blood levels

Question 2

Penicillin V

Answer 2

• Beta Lactam
• Standard narrow spectrum
• G+
• PO
• DOC for syphilis

Question 3

Nafcillin

Answer 3

• Beta Lactam
• Penicillin resistant narrow spectrum
• Used against Pen G resistant staphylococcal (MSSA)

Question 4

Amoxicillin

Answer 4

• Beta Lactam
• Aminopenicillins broad spectrum
• G+
• G- due to increased penetration through porins
• Orally often with B-lactamase inhibitors

Question 5

Ticarcillin

Answer 5

• Beta Lactam
• Antipseudomonal extended spectrum
• Spectrum includes aminopenicillins PLUS Pseudomonas aeruinosa
• Used IV for serious hospital aquired G- infections
• Ticarcillin of large IV dose = Na+ overload = CHF

Question 6

Piperacillin

Answer 6

• Beta Lactam
• Antipseudomonal extended spectrum
• Spectrum includes aminopenicillins PLUS Pseudomonas aeruinosa
• Used IV for serious hospital aquired G- infections

Question 7

Clavulanic Acid

Answer 7

• Beta Lactam
• Fixed dose with B-lactamase inhibitors
• Amoxicillin/Clavulanate
• Ticarcillin/Clavulanate
• Restores spectrum of activity against B-lactamase producing bacteria (but not altered PBPs)

Question 8

Cefazolin

Answer 8

• 1st generation
• G+ MSSA (but not MRSA)
• Commonly used immediately before surgery
• Alternative to Penicillins when mild allergy exists

Question 9

Cefoxitin

Answer 9

• 2nd generation
• G- bacteria
• Largely replaced by 3rd generation

Question 10

Ceftriaxone

Answer 10

• 3rd generation
• G-
• Penetrates into CNS
• Tx meningitis and gonorrhea

Question 11

Cefepime

Answer 11

• 4th generation
• Good CNS penetration
• Empirical Tx of hospitalized pts when resistance due to extended spectrum B-lactamase

Question 12

Imipenem/Cilastatin

Answer 12

• Beta Lactam
• Broad spectrum
• Resistant to B-Lactamase except class A KPC and B NDM-1 carbapenemases
• Parenterally
• Fixed dose to prevent renal inactivation
• Tx for multi drug resisteant infections
• Risk of seizures with Imipenem

Question 13

Aztreonam

Answer 13

• Beta Lactam (but not fused with second ring)
• Narrow spectrum
• G- & Pseudomonas
• IV (poor oral absorption)
• Renal excretion
• Resistant to B-Lactamase (except KPC)

Question 14

Vancomycin

Answer 14

• Glycopeptide
• Reserved for serious infection
• Prevents polymerization of cell wall precursors (binds D-Ala-D-Ala terminus of the NAM monomer)
• Only G+ (too large for G-)
• VRE and VRSA due to D-Ala-D-lactate decreasing binding affinity
• IV (PO if GI infection)

Question 15

Fosfomycin

Answer 15

• Glycopeptide
• Phosphoenolpyruvate analogue
• Tx G- UTIs
• Inhibits production of murein monomers (blocks synthesis of UDP-NAM)
• Enters bacteria via glycerophosphate transporter (not found in host cells)

Question 16

Bacitracin

Answer 16

-Glycopeptide
-Inhibits bactoprenol dephosphorylation (carrier across inner membrane, must be dephos to return to carry another monomer)
-G+
-Acquired resistance uncommon
Available in topical fixed dose with neomycin/polymyxin (neosporin)
-Highly nephrotoxic is admin systemically

Question 17

Pharmokinetics of Beta Lactams

Answer 17

• Not orally well absorbed –> diarrhea
• Short half lives; given frequently
• Blocked by probenecid so concentrations high in urine

Question 18

Adverse reactions of Beta Lactams

Answer 18

• Least toxic of all Abx (pregnancy use ok)
• Jarisch-Herxheimer
• CNS toxicity with high doses
• Repository preps fatal if given IV (benzathine)
• Rashes not allergy related (Amoxicillin)

Question 19

Penicillin Allergy

Answer 19

• Can occur in absence of prior drug exposure (unknown exposure through moldy bread)
• Urticarial rash, fever, bronchospasm, SJS, anaphylaxis
• Immediate hypersensitivity (angioedema/anaphylaxis) may be fatal; Tx with Epi

Question 20

Cephalosporins Overall

Answer 20

From 1st to 5th generation:

• Increasing activity against G-/anaerobes
• Increasing resistance to B-Lactamase
• Increasing penetration into CNS

Question 21

Vancomycin Treatment Uses:

Answer 21

• Parenteral (MRSA)
• Combo with 3rd generation for meningitis
• PO for severe CDAD (used if metronidazole is ineffective)
• Severe G+ alternative to Penicillin

Question 22

Vancomycin Adverse Reactions:

Answer 22

• Ototoxic
• Nephrotoxic
• “red man syndrome” with rapid infusion due to histamine release
• Thrombophlebitis with IV (admin dilute slowly)