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Fluoroquinolones
- Drugs: ciprofloxacin, levofloxacin, gatofloxican, moxifloxican
- Mechanism: inhibition of DNA gyrase (gram negative) and topoisomerase (gram positive) by binding DNA enzyme complexes
- Pharmacokinetics: Excellent oral bioavailability, may be impaired by divvalent cations in antacids
- Distribution: High volume of distribution, not recommended for bacterial meningitis
- Elimination: Mostly renal, dosage adjustment for low creatine clearance
- Adverse effects: nausea, vomiting, diarrhea, photosensitivity; May damage growing cartilage (not used in < 18), tendinitis; small risk of long QT syndromes
- Drug Interactions: Chelated by di/trivalent cations (antacids, vitamins, dairy products)
- Clinical use: Gram negative aerobes (enterpbacteriaceae); newer versions act better than older versions at treating S. Pneumoniae, community acquired pnuemonia
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Metronidazole
- Nitroimidazole
- Mechanism: Enters bacteria via passive diffusion, reductive process creates free radicals that disrupt DNA and stop protein synthesis
- Restricted to anaerobic bacteria and protazoa
- Pharmacokinetics: Oral admin, large volume of distribution, high CSF levels, liver metabolism
- Adverse rxn: High levels of nausea/vomiting, disulferam like rxn with alcohol
- Clinical: gold standard anaerobic agent, best for gram negative like B. Fragilis, drug of choice for C. Diff
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Rifampin
- Mechanism: Inhibits bacterial RNA polymerase
- Pharmacokinetics: Liver metabolism, orange tinge to bodily fluids
- Adverse rxn: Hepatotoxicity, inducer of hepatic enzymes, including glucocorticosteroids, birth control, etc...
- Use: TB, N. Meningiditis and S. Aureus
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Sulfonamides
- Mechanism: comete with PABA for DHPS, inhibiting folate synthesis
- Bacteriostatic
- Only effective in organisms that synthesize own folate
- Can be used alone in Nocardia infection
- Most allergenic of all antibiotics; diffuse maculopapular rash, higher risk in HIV+ people, Steven Johnson's toxic epidermal necrolysis
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TMP/SMZ
- Mechanism: DHFR inhibitor + sulfonamide action
- Bactericidal
- Excreted unchanged by kidney, not indicated for meningitis
- Indications: UTIs, PCP, enterobacteriaceae
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Nitrofurantoin
- Used for UTIs
- Only oral formulation, low serum tissue concentrations but adequate urine concentrations
- Not effective for UTIs with proteus
- Peripheral neuropathy, pulmonary fibrosis with prolonged use
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