Exam 1: Antimicrobials and Antibiotics Flashcards
Class of antibiotic to use in immunocompromised patients:
Bactericidal
Reason for preserving normal/GI flora if possible:
Normal flora have antixenobiological action
Type of abx usually used in OR:
Cheap, broad spectrum
Are abx always necessary in OR?
No; pts with allergies and superficial surgeries may not need
SCIP guidelines for abx:
Single dose within 1 hr of incision
Considerations for selection of abx:
ID of causative organism
Drug delivery to site
Single drug if possible
Route, duration, cost
Pts who particularly need prophylactic abx:
Bowel/appy
Hardware
Diabetics
Extended surgical time
Relationship between hypersensitivity reaction and dose:
Independent
Relationship between drug toxicity and dose:
Dose related
Abx concerns with parturients:
Most abx cross the placenta and enter milk
Possible teratogenicity
Abx concerns with elderly:
Renal impairment
Decreased plasma protein
Reduced GI mobility, acidity
Increased body fat = more drug in tissues
Penicillin structure and mechanism of action:
Bactericidal beta-lactam
Interferes with bacterial cell wall
Organisms susceptible to penicillin:
-coccals
Pneumococcal
Meningococcal
Streptococcal
Penicillin elimination:
Renal
Ampicillin organisms:
Gram(-)
H. influenza, e. coli
Notable ampicillin adverse effect:
Skin rash
Amoxicillin advantage over ampicillin:
More efficiently absorbed from GI tract
Most allergenic antimicrobial:
Penicillins
Most common adverse reaction to PCNs:
Allergy/hypersensitivity
Signs of PCN allergy:
Rash and/or fever
Anaphylaxis
Hemolytic anemia
Classes of abx with cross-sensitivity and % chance:
PCNs and cephalosporins
8% chance
Cephalosporin mechanism of action:
Bactericidal
Inhibits bacterial cell wall synthesis
Cephalosporin elimination route:
40% bile
60% renal
Cephalosporin organisms:
Broad spectrum
Primary s/s of cephalosporin allergy:
Rash
% incidence of anaphylactic rxn to cephalosporin:
0.02%
First, second, and third generation cephalosporins:
1st: cefazolin
2nd: cefoxitin
3rd: cefotaxime
Type of surgery that often uses cephalosporins and why:
Ortho - cephalosporins penetrate into joints
Differences in cephalosporin generations:
Better anti-Gm(-) activity in later generations
Aminoglycoside mechanism of action:
Bactericidal
Inhibits cellular activity inside microbe
Aminoglycoside organisms:
Aerobic Gm(-)
Aminoglycoside elimination & elimination half-time
Extensively renal
2-3hr elimination half-time in healthy pt
20-40x increase in renal failure
Aminoglycoside adverse effects:
Ototoxicity
Nephrotoxicity
Skeletal muscle weakness
Prolongs NMB
Mechanism of aminoglycoside ototoxicity:
Irreversible damage to vestibular/cochlear hairs
Dose dependent
Mechanism of aminoglycoside nephrotoxicity:
Accumulation in renal cortex –> tubular necrosis –> proteinuria, dilute urine, RBC casts
Reversible!
Most nephrotoxic aminoglycoside:
Neomycin (mostly given topical for this reason)
Mechanism of aminoglycoside muscle weakness:
Inhibits pre-synaptic ACh release
Decreases post-synaptic sensitivity to ACh
Patient population in whom aminoglycosides should be avoided:
Myasthenia gravis
“Sneaky” way aminoglycosides become systemically absorbed:
From irrigation fluid
Drug effect enhanced by aminoglycosides:
NM blocking properties of lidocaine
Five aminoglycosides:
Streptomycin Kanamycin Gentamicin Amikacin Neomycin
Toxic level of gentamicin:
> 9mcg/ml