Lecture 16: Antibiotics Part 2 Flashcards by Emily Wood

Are all DNA synthesis agents bactericidal or bacteriostatic?

Bactericidal

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What do all fluoroquinolones end in?

Floxacin

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What are the main 3 FQs used in clinical practice?

Ciprofloxacin
Levofloxacin
Moxifloxacin

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What is the MOA of a FQ?

Inhibits bacterial DNA topoisomerase and gyrase, promoting DNA breakage

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What is unique about the spectrum of an FQ?

Atypical coverage

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If I want anaerobic coverage in an FQ, which one would I choose?

Moxifloxacin

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When I see respiratory FQs, what am I referring to?

Levofloxacin, Moxifloxacin, and Gemifloxacin.

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When I see antipseudomonal FQs, what am I referring to?

Levofloxacin, Ciprofloxacin

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What do FQs generally lack coverage of?

Staph A

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What is the novel FQ that can cover MRSA?

Delafloxacin

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What is the major concern when prescribing an FQ to the elderly?

CNS effects.

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Which FQ does not have QT prolongation concerns?

Delafloxacin

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What bacterial GI effect is heavy FQ use associated with?

C. Diff diarrhea

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What is the BBW of an FQ?

Tendonitis/Tendon rupture

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What is the MOA of metronidazole?

Cause loss of DNA helical structure and strand breakage

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What drug class is metronidazole?

Nitroimidazole

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What is the coverage of metronidazole?

Anaerobes only

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What is metronidazole often combined with?

Levofloxacin, since levofloxacin has poor anaerobic coverage.

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What is the BBW of metronidazole?

Carcinogen!!
DO NOT DRINK WITH ALCOHOL

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How many weeks of metronidazole therapy do I start to see CNS toxicity?

4 weeks

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What kind of drug-drug interactions does metronidazole have?

Increase warfarin and lithium
Decreased by phenobarbital and phenytoin, and increased by cimetidine

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What is the MOA of rifampin?

Inhibits beta-subunit of DNA-dependent RNA polymerase

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What is rifampin’s main clinical use regarding staphylococcus?

Used as synergistic therapy. It prevents staph A from sticking to prosthetics like heart valves or limbs.

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What are the 3 bacteria rifampin is mainly used for?

Staphylococcus
Mycobacterium
Neisseria

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What is the main side effect that I need to counsel patients about regarding rifampin?

Red-orange staining for body fluids!

What are the side effects of extended rifampin usage > 4 weeks?

Hematologic effects (Thrombocytopenia, leukopenia, and granulocytopenia)

What should I always do when attempting to order rifampin?

Drug interaction check!!!!!

What medications does rifampin have proven interference with?

Oral contraceptives.

What are the two folate antagonists?

Sulfamethoxazole Trimethoprim

What bacteria are the folate antagonists the drug of choice for?

Stenotrophomonas maltophilia

What are folate antagonists known for causing more frequently than most other abx? (side effect)

SJS/TEN Steven johnson syndrome Toxic epidermis necrolysis AKA RASH

What hypersensitivity reaction should I be wary about regarding folate antagonists?

Sulfa allergies.

What kind of drugs should I be wary about when adding a folate antagonist?

Any drug that can cause hyperkalemia as well.

What kind of patients must avoid folate antagonists?

G6PD deficiency

What are the protein inhibitors?

30S: Tetracyclines Glycylcyclines 30S & 50S: Aminoglycosides 50S: Macrolides Lincosamides Streptogrammins Oxazolidinones

Are protein inhibitors bacteriostatic or bactericidal?

Bacteriostatic, aka inhibition of growth but does not kill bacteria.

What are the 3 tetracycline drugs?

Tetracycline Doxycycline Minocycline

What can tetracyclines cover that is significant?

Atypicals!

What drug can treat MDR acinetobacter?

Minocycline

What are tetracyclines absolutely contraindicated in?

Pregnant women and children < 8 yo because of teeth discoloration (permanent)

Which of the tetracyclines is the most well-tolerated?

Doxycycline

What causes impaired absorption of tetracyclines?

Vitamins, such as products with Ca, Fe, Mg, Al, or Zinc.

What drug is a glycylcycline?

Tigecycline (tiger!)

What is the common clinical use of tigecycline?

Second-line. Note: Very broad spectrum agent.

What is unique about the PK of tigecycline?

Rapid tissue periphery distribution. This means it is also useless for bacteremia.

What is the main adverse effect that took tigecycline off primary use?

GI effects (30%!!!)

What is unique about the new tetracyclines' coverage?

Cover atypicals!

What are the two new tetracyclines?

Omadacycline Eravacycline

What are the 3 aminoglycosides?

Gentamicin Tobramycin Amikacin

Why are aminoglycosides commonly used in combination?

Monotherapy can cause resistance to build up very fast. They also don't have great G+ coverage.

What toxicity should I be wary about in aminoglycosides? why?

Nephrotoxicity, because they build up in the urine.

What is the new aminoglycoside?

Plazomicin

What is the spectrum of plazomicin?

S. Aureus + MRSA CRE

What are the 3 macrolides?

Erythromycin Azithromycin Clarithromycin ACE mycins

What is unique about the coverage of macrolides?

Atypical coverage!

Why is erythromycin generally not used as an ABX anymore?

GI side effects.

Why do we prefer azithromycin among the macrolides?

No interaction with CYP 3A4.

What drugs should I avoid when using macrolides?

QT prolonging drugs warfarin

What are the two treatments for C. Diff?

Vancomycin + Fidaxomicin

What is the MOA of fidaxomicin?

Inhibits RNA synthesis via RNA polymerase inhibition

What drug is a lincosamide?

Clindamycin

What is the boxed warning for clindamycin?

Pseudomembranous colitis

What drug is a streptogrammin?

Quinupristin-dalfopristin

Why do we not use streptogrammin anymore?

Myalgia

What drugs are oxazolidinones?

Linezolid Tedizolid

What is significant about oxazolidinones?

G+ only, includes MRSA and VRE. One of only 2 drugs? that is reliable for VRE treatment.

What is the most common adverse reaction with linezolid usage > 2 weeks?

Thrombocytopenia Myelosuppression

What adverse reaction can occur with linezolid usage > 4 weeks?

IRREVERSIBLE peripheral neuropathy! and optic neuropathy.

Why is unique about the PK of linezolid?

PO bioavailability is the same as IV.

What is an interaction that we should still counsel pts about regarding linezolid?

Serotonin syndrome (which is proven to be not be the case anymore)

What drug is a pleuromutilin?

Lefamulin

What is significant about the spectrum of lefamulin?

Atypical coverage

What drugs are lefamulin CId with?

QT prolonging drugs

What is the MOA of nitrofurantoin?

Reduced by flavoproteins to active intermediates that may inactivate or damage ribosomal proteins, DNA and RNA

What is unique about the MOA of nitrofurantoin?

ONLY active in urine! Needs CrCl > 30

What is the main use of nitrofurantoin? Why?

E. Coli causing UTIs in elderly because it is well-tolerated and works only in urine.

What disease is caused by long-term use of nitrofurantoin?

Pulmonary fibrosis

What is the MOA of fosfomycin?

Interferes with bacterial cell wall synthesis by inhibiting enolpyruvyl transferase. Active in urine only.

Why is fosfomycin not used frequently even though it has a broad spectrum?

G- bacteria can produce products that inactivate fosfomycin.

Describe the treatment modality for pseudomonas aeruginosa.

Empiric double-coverage. Choose one of the beta lactams: ES penicllin: Pip-tazo 3rd gen cephalosporin: Ceftazidime 4th gen cephalosporin: Cefepime Carbapenems: Doripenem, Imipenem-cilastatin, meropenem Monobactam: aztreonam (Doripenem no longer used clinically. Then Choose one of the FQs or aminoglycosides: Antipseudomonal FQs: Ciprofloxacin, Levofloxacin Aminoglycosides: Amikacin, Tobramycin, Gentamicin Note: FQs are preferred over aminoglycosides due to nephrotoxicity.