Week 2 - Antimicrobials

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Week 2 - Antimicrobials
2013-06-21 16:18:59

antibiotics drugs resistance
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  1. Antibiotic Selection
    • Patient history
    • site of infection
    • Likely causative agent (get culture)
    • Lab results (WBC level, etc.)
    • Isolation and Identification (gram stain; culture from sputum, wound, urine, blood, stool)
  2. Bactericidal
    chemical substances that KILL microorganisms
  3. bacteriostatic
    chemical substances that SUPPRESS growth of microorganisms
  4. Major principles
    • -kill the bugs, not the host is the idea
    • -select the narrowest spectrum agent possible
    • -Less impact on the good/beneficial bacteria in the body
    • -Killing everything leads to antibiotic resistance (those partially killed will evolve or things normally beneficial may become pathological)
  5. Two major categories of drugs
    • Work over time: dosing around clock, must keep even concentration of drug over several days, and needed for "thick cell" (Gram +) bacteria
    • Concentration dependent: Need enough to destroy DNA of bacteria; can be a once or twice daily dosing
  6. Administration
    • Oral most common
    • IM when shorter term administration (deltoid or gluteus for best absorption and least irritation)
    • IV for most serious infections (must be given w/in 1/2 hour of designated due time (imp to keep specific level in blood)
  7. Superinfections
    • those that occur during or after admin of antimicrobial therapy
    • most common w/ broad spectrum antibiotic that also affects normal flora
  8. Penicillins
    • Prototypes: penicillin G and V, methicillin, ampicillin
    • Action: act on developing bacterial cell wall making it susceptible to osmotic pressure and it explodes
    • -most effective against gram + bacteria
    • -contain a beta-lactam ring that is essential to its antibiotic abilities (B-lactam group)
    • Side effects: allergic rxns (<5%) like hives, fever, chills, GI: N/V/D, Renal
    • PCN is easily excreted from kidneys; If given w/ Probenecid (drug that increases uric acid excretion in the urine), excretion of PCN is blocked (HELPFUL interaction!)
  9. Aminopenicillins
    • Prototope: Ampicillin amoxicillin
    • Indications: Useful in selected gram-neg bacteria so broader spectrum but not penicillinase (enzyme produced by bacteria that inactivate penicillin) resistant
  10. Cephalosporins
    • chemical modifications of the penicillin structure (inhibits cell wall synthesis)
    • Divided into 4 generations 
    • SE: GI, superinfections, allergic rxn, candidiasis, rash, edema
  11. Macrolides
    • Prototypes: erythromycin, azithromycin (Zithromax), clarithromycin (Biaxin)
    • Inhibit protein synthesis (bacteriostatic)
    • Indications: oral and topical, drug of choice for many respiration infections; one of least toxic and few allergies
    • SE: GI symptoms
    • Foods can decrease absorption (but have to b/c people get queasy)
  12. Vancomycin (Vancocin)
    • Binds to cell wall precursors, leads to cell lysis (bactericidal) 
    • Used for serious staph infections of bone, joint, septicemia, MRSA strains, prophylaxis for endocarditis 
    • SE: N/V, metallic taste, "red neck" syndrome (histamine flush) if IV admin too rapid
    • -peak and trough med
  13. Aminoglycosides
    • SE: nephrotoxicity, ototoxicity (kills sensory cells of inner ear)
    • Overdose: Neuromuscular blockade; CHECK drug levels (peak and trough at certain times) by drawing blood for levels... results determine when next dose will be administered
    • Gentamicin is an aminoglycoside antibiotic, used to treat many types of bacterial infections, particularly those caused by Gram-negative organisms.
  14. Tetracycline
    • Prototype: tetracycline & doxycycline 
    • Inhibits protein synthesis (bacteriostatic) 
    • Indications: Chlamydia, Lyme disease, Acne
    • Oral ONLY.. do NOT mix with milk, antacids, or iron supplements
    • Contraindications: pregnant and breastfeeding women, children under 8 (permanent staining of teeth and decreases growth)
    • SE: most common is GI tract (local irritation and oral candidiasis and Oral candidiases), Photosensitivity
    • Class very useful in RARE things (Plague, Cholera, Atypical bacteria, rabbit fever)
  15. Fluoroquinolones
    • Prototype: ciprofloxacin (Cipro) 
    • synthetic, broad spectrum, bactericidal by altering bacterial DNA
    • Wide distribution in body (used for pseudomonas, anthrax)
    • Popular for UTIs, but not anymore.. saving for bigger problems
    • Makes tendons rupture, weaker, ache, pain
    • Can't take with Ca, Zn, Fe, Al, or Mg
    • Never given to pregnant patients of children!
  16. Sulfonamides
    • Prototype: TMP-SMX (Bactrim)
    • Synthetic
    • interfere with bacterial enzymes
    • Bacteriostatic 
    • Interferes with folic acid metabolism
    • good absorption, take on empty stomach
    • Indications: used for UTIs and MRSA
    • *A lot of people are genetically allergic to sulfa drugs.
    • SE: GI, bone marrow toxicity, allergic rxns common, hematologic effects if long-term therapy, Steven's Johnson Syndrome
    • Must drink a lot of water with sulfa drugs
  17. Antiviral drugs
    • Used alone or in combination
    • Indications: Herpes simplex 1 (cold sore), herpes zoster (shingles), genital herpes (herpes simplex ll), varicella, influenza, RSV, HIV
  18. Herpes and Varicella
    • Prototypes: acyclovir (Zovirax), famciclovir (Famvir)
    • Action: interferes with DNA replication
    • Use: needs to be initiated w/in 24 hrs of onset of s/s
    • available in PO, IV, and topical forms
    • Poor absorption PO, so you're taking a lot more than being used at cellular level
  19. Influenza
    • Prototype: amantadine
    • Action: Blocks uncoating of the influenza A (not B or swine or chicken flus) virus and the release of viral nucleic acid into host cell
    • Rapid absorption, wide distribution (crosses BBB) 
    • Viruses have gotten smart and now resistant to this med... now have tamiflu.
  20. Oseltamivir (Tamiflu)
    • In news as Bird Flu drug
    • Start as early as possible (probably wont' work)
    • Take even if feel better
    • NOT a substitute for a flu shot
    • May decrease length of illness by a day
    • now last year's flu and bird flu are resistant
  21. HIV
    • composed of RNA which is translated to DNA by reverse transcriptase enzyme in order to reproduce
    • Integrated DNA then becomes part of the cell's DNA and produces proteins for assembly of new HIV 
    • Cannot be cured.. only suppress symptoms
    • Drugs used: reverse transcriptase and protease inhibitors
    • Ongoing HIV replication leads to immune system damage and progression to AIDS
    • Plasma HIV RNA levels (viral load) indicate magnitude of HIV replication and its rate of CD4 T-cell destruction (CD4 counts tell us extent of damage); some cocktails may make viral load = 0, but will come back if stop meds
    • At minimum therapy begins when CD4 count <500 or plasma HIV RNA levels >5,000-100,000
  22. SE of HIV medication
    • Lactic acidosis: can be fatal - N & V
    • Lipodystrophy syndrome (fat distribution, hepatotoxic, peripheral neuropathy, pancreatitis, fatigue)
  23. Drugs used in treatment of Opportunistic infections
    • Anti-TB meds (anti-virals make you more susceptible to TB)
    • Anti-fungal meds (thrush, severe vaginitis, severe rashes)
    • anti-herpes drugs 
    • chemotherapy (more likely to get cancer on HIV drugs)