Other antibiotics Flashcards
Quinolones inhibit:
• DNA gyrase • Topoisomerase IV
4 Quinolones end in_
Ciprofloxacin, Levofloxacin, Moxifloxacin, Norfloxacin
Quinolones Resistance Mechanisms:
Alterations of DNA gyrase and topoisomerase IV • Alteration in cell permeability • Efflux of drug
3 Common clinical uses (adults only) of Quinolones:
Common clinical uses (adults only)
UTIs (E. Coli, other enteric gram negatives)
Pneumonia (S. pneumo, H. flu, atypicals)
Abdominal infections (enteric gram negatives)
Quinolones Early Drugs
Nalidixic acid (not a fluoroquinolone), Norfloxacin • Mostly gram negative coverage • Limited/no gram positive coverage
Quinolones Ciprofloxacin:
• Some gram positive coverage • Rarely used alone for gram positive coverage (resistance)
Very good gram negative coverage
Most reliable pseudomonas coverage
Used in UTIs, GI infections • Cipro ear drops for otitis externa
Quinolones Levofloxacin:
commonly used in:
• More gram positive/atypical coverage than Cipro • Better strep pneumo coverage than Cipro • Covers most methicillin-susceptible Staph aureus • Less effective against pseudomonas than Cipro • Commonly used in pneumonia (strep, atypicals)
Quinolones Gatifloxacin, Sparfloxacin, Moxifloxacin
• Better gram (+)/atypical coverage than Levofloxacin • Less effective for pseudomonas than Levofloxacin • Also used in pneumonia
Quinolones Adverse Reactions:
rare/serious complication:
generally well tolerated but: Gastrointestinal upset • Anorexia, nausea, vomiting, and abdominal discomfort • Up to 17% of patients • Neurologic side effects • Headache, dizziness • 2 to 6% of patients
QT prolongation on EKG • Caused by blockade of K+ channels • Can lead to torsade de pointes
Quinolones Adverse Reactions why can’t be used in kids/pregnancy?
Cannot use in pregnancy/children • Toxic to developing cartilage in animal studies
Tendon rupture/tendonitis • Most commonly Achilles • More common older patients (>60), people on steroids
Antacids • Disrupt absorption of many drugs including:
• Key drugs • Tetracycline • Fluoroquinolones • Isoniazid • Iron supplements
Vancomycin MOA:
contrast with beta lactams:
• Inhibits peptidoglycan formation (cell wall)
Binds D-alanyl-D-alanine peptides • Prevents crosslinking • Cell wall breakdown>formation → cell death
Same effect as beta lactams via different mechanism • Beta lactams: inhibit transpeptidases • Vancomycin: block transpeptidase binding
Vancomycin Resistance:
terminal amino acids change • D-alanyl-D-alanine changed to D-alanyl-D-lactate • VRSA emerges
Vancomycin only effective in:
gram (+) • Too large to pass outer membrane gram negatives
Two common uses: of Vancomycin:
2: Oral therapy for C. difficile pseudomembranous colitis
• #1: Methicillin resistant Staph Aureus (MRSA)
Often given empirically when MRSA is a concern • Endocarditis • Severe pneumonia/sepsis
Vancomycin Adverse Effects
Nephrotoxicity • Less common with modern preparations • Increased risk if concomitant aminoglycoside therapy
Ototoxicity • Tinnitus, vertigo, and hearing loss reported (rare)
• Vancomycin infusion reaction • Flushing, erythema, itching • Usually affects upper body, neck, face more than lower body • Occurs 10-20 minutes after start of infusion • Direct activation of mast cells → histamine release • “Pseudoallergic drug reaction” • May develop with first administration
Infusion related → slow infusion = no symptoms
Metronidazole: whats needed for activation?
Prodrug: Must be reduced to activate
Only anaerobic bacteria capable of reduction
Activated form generates free radicals • Interact with DNA • DNA breakage/destabilization • Cell death
Metronidazole Uses
• Good coverage of anaerobes “below the diaphragm”
Bacteroides fragilis • Clostridium difficile
Peritonitis, abdominal abscesses, diverticulitis
Often given with quinolone for anaerobic/GI gram(-) • Cipro/Flagyl often used for diverticulitis
2 main Metronidazole Uses
• H. pylori and Gardnerella vaginalis • Facultative anaerobic bacteria • Susceptible to metronidazole • Triple therapy for H. Pylori • Treatment of bacterial vaginitis
Anaerobic protozoa covered by Metronidazole
Anaerobic protozoa (lack mitochondria) • Trichomonas vaginalis • Entamoeba histolytica • Giardia lamblia
Metronidazole Adverse Reactions
Unpleasant metallic taste • GI: Abdominal discomfort, nausea • Neuro: Neuropathy, headache
Disulfiram-like reaction Patients should avoid alcohol
whats Used for UTIs in pregnancy? & 3 things to know about it
Nitrofurantoin
- Bactericidal drug
- Only use is UTIs (concentrates in urine)
- Can trigger hemolysis in G6PD patients