DD - Anti-Bacterial Agents - Details

Question 1

Penicillin G

Answer 1

Prototype penicillin

MOA: cell wall synthesis inhibitor
PK: renal excretion, IM/IV administration
Spectrum/Uses: gram + cocci (staph/strep/entero), gram - cocci (neisseria, M. catarrhalis), gram - rods, anaerobes (NOT Bacteroides)
Adverse reactions: anaphylaxis (Type I), rash, convulsions (w/ high doses)

Question 2

Penicillin V

Answer 2

Acid-stable penicillin

MOA: cell wall synthesis inhibitor
PK: good oral absorption, renal excretion
Spectrum/Uses: gram + cocci (Staph/Strep/Entero), gram - cocci (Neisseria, M. catarrhalis), gram - rods, anaerobes (NOT Bacteroides)
Adverse reactions: anaphylaxis (Type I), rash, convulsions (w/ high doses)

Question 3

Dicloxacillin

Answer 3

Penicillinase-resistant penicillin

MOA: cell wall synthesis inhibitor
PK: good oral absorption, renal excretion
Spectrum/Uses: Penicillinase-producing S. aureus (MSSA) skin infections (NOT MRSA)

Question 4

Amoxicillin (+/- Clavulanate), Ampicillin

Answer 4

Extended spectrum penicillins

MOA: cell wall synthesis inhibitor
PK: good oral absorption, renal excretion
Spectrum/Uses: gram - rods (H. flu, E. coli, Proteus), gram + cocci (but less than Penicillin G/V)
Adverse reactions: diarrhea (less with amoxicillin), superinfection (CDAD) possible

Question 5

Piperacillin (+/- Tazobactam)

Answer 5

Anti-pseudomonal penicillins

MOA: cell wall synthesis inhibitor
PK: IV only administration, renal excretion
Spectrum/Uses: Pseudomonas, Bacteroides (and other anaerobes)

Question 6

Clavulanic acid

Answer 6

Beta-lactamase inhibitor

MOA: cell wall synthesis inhibitor

Question 7

Cefazolin, Cephalexin

Answer 7

1st generation cephalosporins

MOA: cell wall synthesis inhibitor
PK: Cefazolin IV/IM only, Cephalexin good oral absorption; renal excretion
Spectrum/Uses: gram + cocci, gram - rods (Proteus, E. coli, Klebsiella)
Adverse reactions: diarrhea

Question 8

Cefuroxime

Answer 8

2nd generation cephalosporins

MOA: cell wall synthesis inhibitor
PK: good oral absorption; renal excretion
Spectrum/Uses: gram - rods (H. flu, Enterobacter), Bacteroides (and other anaerobes)
Adverse reactions: DDI - enhancement of warfarin anticoagulant activity possible; superinfection (CDAD) possible

Question 9

Ceftriaxone

Answer 9

3rd generation cephalosporins

MOA: cell wall synthesis inhibitor
PK: good CNS penetration, IV/IM administration; renal excretion
Spectrum/Uses: expanded gram - rods, good gram + cocci, moderate antipseudomonal
Adverse reactions: superinfection (CDAD) possible

Question 10

Vancomycin

Answer 10

MOA: Cell wall synthesis inhibitor, stage 2 bactericidal
PK: poor oral absorption; renal excretion
Spectrum/Uses: narrow spectrum, Gram + cocci. Active against MRSA, enterococci, C. diff anaerobe
Adverse reactions: infusion related fever/chills/rash, ototoxicity, renal toxicity. Needs routine monitoring of Cp levels.

Question 11

Erythromycin, Clarithromycin, Azithromycin

Answer 11

Macrolides

MOA: 50S protein synthesis inhibitors, bacteriostatic
PK: Generally good oral and IV absorption. Concentrates in lungs. Specifically, Erythromycin QID, liver metabolism; Clarithromycin BID, metabolized to active metabolite; Azithromycin QD, biliary excretion.
Spectrum/Uses: gram + cocci/rods (alternative if allergic to penicillin), some gram - bacilli (Legionella, Bordetella, H. pylori), mycoplasma/chalmydia pneumonia
Adverse reactions: GI disturbances (n/v, diarrhea), DD interactions due to INHIBITION of P450 metabolism for erythromycin, clarithromycin (not azithromycin)

Question 12

Tetracycline, Doxycycline

Answer 12

Tetracyclines

MOA: 30S protein synthesis inhibitor, bacteriostatic
PK: Tetracycline orally, renal excretion. Doxycycline orally, biliary excretion (non-renal).
Spectrum/Uses: broad spectrum BUT many gram +/- organisms are now resistant. Choice in CA-MRSA, good activity for chlamydia, mycoplasma, rickettsia, spirochetes
Adverse reactions: abnormal bone/tooth development (avoid in pregnancy and children < 8 years old), n/v/diarrhea, fungal superinfection, DD interactions with metal cations (antacids/dairy/iron) in stomach

Question 13

Clindamycin

Answer 13

Lincomycin

MOA: 50S protein synthesis inhibitor, bacteriostatic
PK: good PO, also IV, penetrates into bone, hepatobiliary excretion
Spectrum/Uses: narrow spectrum. Gram + cocci (PCN alterative), anaerobes (NOT C. diff), acne (topically), choice in CA-MRSA
Adverse reactions: severe diarrhea, pseudomembranous colitis

Question 14

Chloramphenicol

Answer 14

Synthetic agent

MOA: 50S protein synthesis inhibitor, bacteriostatic
PK: good PO, also IV. Distributes to CNS/CSF, metabolized by glucuronidation
Spectrum/Uses: broad spectrum, gram +/- cocci (H. flu, Neisseria [meningitis]), anaerobes, Rickettsia
Adverse reactions: bone marrow toxicity, gray baby syndrome, GI upset. Toxicity limits use in USA.

Question 15

Aminoglycosides (class)

Answer 15

MOA: 30S Protein synthesis inhibitors, bactericidal
PK: poor oral absorption (IV/IM administration), distributed in extracellular fluid, accumulates in kidney/inner ear, renal excretion
Spectrum/Uses: narrow spectrum. Gram - aerobes (E. coli, Pseudomonas)
Adverse reactions: vestibular and auditory toxicity, nephrotoxicity, routine monitoring of Cp levels necessary.

Question 16

Ciprofloxacin, Levofloxacin, Moxifloxacin

Answer 16

Quinolones & Floroquinolones

MOA: inhibition of DNA function, inhibition of DNA gyrase, bactericidal
PK: good oral, also IV. Ciproflaxin (2nd gen) & Levofloxacin (3rd gen) primarily renal excretion; Moxifloxacin (4th gen) primarily hepatic (20% renal)
Spectrum/Uses: Extended spectrum. Ciproflaxin excellent gram - (Pseudomonas, UTIs); Levofloxacin excellent gram +/- (respiratory, UTIs); Moxifloxacin excellent gram +/- (respiratory, plus some anaerobes)
Adverse reactions: well tolerated, some GI upset, superinfections (CDAD) possible, DDI with theophylline (decreased metabolism) and antacids (decreased FQ absorption). Rare: CNS disorders, increased QT interval. Not 1st choice in children (potential arthralgias).

Question 17

Nitrofurantoin

Answer 17

MOA: Inhibition of DNA function, reduced in cell to intermediates that damage bacterial DNA, bactericidal
PK: rapid, complete GI absorption but rapid excretion via kidneys, thus acts as urinary antiseptic
Spectrum/Uses: 1st line agent in UTIs if TMP-SMX resistant E. coli
Adverse reactions: GI side effects, macrocrystalline forms better tolerated

Question 18

Metronidazole

Answer 18

MOA: Inhibition of DNA function, reduced intracellularly to active form; interference with DNA function bactericidal
PK: good oral bioavailability; hepatic metabolism
Spectrum/Uses: anaerobic bacteria (C. diff), protozoa (trichomoniasis, amebiasis, giardiasis)
Adverse reactions: nausea, headache, GI distress, Antabuse-like reaction, occasional candidal superinfections