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