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AntibioticsChapter 16 Notes
Antibiotic Mechanism
of Action
Inhibition of Bacterial
Cell Wall Synthesis
Inhibition of Bacterial
Nucleic acid synthesis
Inhibition of Bacterial Folic Acid Synthesis
Inhibition of Bacterial Protein
Synthesis
Vancomycin
Imipenem/MeropenemPenicillins
Aztreonam
Cephalosporins
Trimethoprim
Sulfonamides
Pyrimethamine
Fluoroquinolones Rifampin
Macrolides
Aminoglycosides
Chloramphenicol
Tetracyclines
Streptogramins
Clindamycin
Linezolid
Beta-lactam Antibiotics “-cillin”
• Inhibits cell wall synthesis. Cell dies by lysis.• Penicillins (types)
• Natural penicillins• Penicillinase-resistant penicillins• Aminopenicillins• Extended-spectrum penicillins
• Carboxypenicillins• Ureidopenicillins
Penicillins - Points
• First ABT on market• Tx: URI, skin• Decreases effectiveness of oral contraceptives – use a condom. • Decreases effectiveness of Coumadin.• Not compatible w/Aminoglycosides (Gentamicin)• Reduces effect of Tetracyclines• Take on empty stomach w/ 8 oz. H2O.
Cephalosporins
• Broader in spectrum than PCN• Ancef, Keflex, Rocephin• Tx: Staph infections• Don’t give with PCN/PCN allergy
• Stable against beta-lactamases.• Categorized by generation• I. Surgical prophylaxis, upper resp. infections, ear infections
• II. Abdominal/ colorectal prophylaxis surgeries
• III. Bacteria meningitis
• IV. Complicated urinary tract infections, uncomplicated skin infections
Trade NamesI. Keflex II. Ceftin III. RocephinIV. Maxipime
Carbapenems “-penem”
• Imipenem/meropenem• Broad spectrum – mixed aerobic/anaerobic• Extended-spectrum beta-lactamases (ESBLs)• #1 concern = drug sensitivity• Avoid with known/likely C. difficile
• Risk: Seizures• Nephrotoxicity/neurotoxicity/immunomodulation • Monitor for abscess/inflammation/phlebitis/rash• Monitor liver function
• May lead to superinfection
Carbapenem-Resistant Enterobacteriaceae (CRE)
Monobactams
• Aztreonam (only one available in U.S.)• Treats: UTI, dermal infection, septicemia, intra-abdominal,
gynecologic infections.• Moderately severe systemic infections and urinary tract infections • Admin IV or IM• Contraindicated in pregnancy
Beta-lactamase inhibitors
• Adjunct therapy only - not useful alone• Amoxicillin/Clavulanic acid (Augmentin)
Sulfonamides
• Target folic acid synthesis.• Inhibit dihydropterate synthetase (enzyme)• May blood glucose levels• Avoid sun exposure• Classifications
• Rapid absorption/excretion• Poor absorption• Rapid absorption/slow excretion• Topical
Tetracyclines
• Doxycycline/Minocycline• Derived from soil mold• Broad spectrum (Gram +/-)• Bacteriostatic• 90-100% bioavailable• Decrease effectiveness PCN G & OBC (oral birth control)• Take on empty stomach w/ 8 oz. H2O.• Report black, furry tongue
Aminoglycosides “-micin,-mycin”
• Gentamicin (Peak: 5-10 mcg/mL)• Tx: Septicemia, infective endocarditis• Narrow-spectrum • Bactericidal • Gram-negative bacteria• Neomycin
• Tx: Cirrhosis • Nephrotoxicity/Ototoxicity
• GFR & serum creatinine
MacROlides “-Romycin”
• Erythromycin -Safest ABT available• Azithromycin “Z-pack”• Bacteriostatic/bactericidal• Very effective against staph. aureus• Better patient compliance • Avoid sun / Take on empty stomach• AVOID in patients with cirrhosis/hepatitis
Quinolones/Fluoroquinolones “-floxacin”• Cipro/Levaquin
• Bactericidal• Tx: UTIs, STDs, GI, abd, respiratory, bone/joint, soft tissue• Orally, parenterally, topically• Avoid/limit caffeine• Excreted by kidneys• No antacids within 4 hours• Monitor urine pH• Increase fluids 2-3L/day• Admin IV slowly – may drop B/P.
Lincosamides
• Clindamycin• Tx: bacterial/protozoan pathogens• Hypersensitivity is rare• Good alternative for PCN allergy/tolerance• Nasty side effect: Pseudomembranous colitis (2-9 days)
Vancomycin
• Bacteriocidal• IV – serious nonresponsive infections (MRSA)• Contraindicated in pregnancy• Nephrotoxic• Peak/Trough – 80-100 mg/mL
*Red man’s syndrome*-infusing too quickly
Oxazolidinones
• Linezolid (synthetic)• Oral/IV• Tx: VRE/MRSA• Avoid foods containing tyramine• No breastfeeding• Avoid caffeine & ETOH• Serious CNS reaction – Serotonin Syndrome• Excreted in urine
Anti-infective drugs – Resistant infections• Streptogramins
• Quinupristin/Dalfopristin – Syndercid• IV admin• Tx: resistant VRE, MRSA• Excreted via bile/feces
Antitubercular drugs
• Isoniazid (INH)• Prophylaxis/combo with other anti-TB meds• Food interferes with absorption• ETOH increases chance liver damage• Antacids interfere with absorption
• Rifampin • Drug of choice: Pulmonary TB – combo drug• Use additional contraception• Caution with alcoholics