module 12 principles of anti-microbial therapy Flashcards
antibiotics
agents produced naturally by microorganisms to suppress the growth of or to kill other organisms.
antimicorbials
include all antibiotics and synthetic preparations
cidal
agents kill bacteria
- immunocompromised patients
- hard to reach areas by the hose immune system
static
suppress growth of but not kill bacteria
- host defense mechanisms help to eliminate infecting organisms
factors affecting antimicrobial selection
identification susceptibility anatomic site pharmacokinetics allergies age pregnancy host defense
pharacokinetics and abx
hepatic vs renal elimination
CYP450 genetic variations: inc. or dec. metabolism
age and abx
young and very old have dec. metabolic pathways and greater potential for toxicity
prophylaxis
abx given to a “healthy” pt to prevent infection
- meningitis
- damaged heart valves
- immunocompromised
- neutropenia: cancer
- GI surgery
- Recurrent UTI
risks with prophylaxis tx
superinfection: fungal
selection of resistant flora
selection of resistant pathogenic organisms
combining abx: indifferent
1+1=2
activity together equals sum of separate independent activities.
combining abx: synergism
1+1=3
activity together is greater than sum of of independent activities
combining abx: antagonism
1+1=1 or <1
activity together is less than the sum of the independent activities
When to consider combo abx
life-threatening infections
polymicrobial infection
desired synergistic effect
prevent of emergent resistant organisms: TB
mechanisms of resistance
due to altered targets - abx no longer works at site of action due to dec. accumulation - organisms creates ways to inhibit abx due to enzymatic inactivation of drug - organism creates enzyme to destroy abx
anti-infective PD
relationship between organsim susceptibility and pt-specific PK
peak/MIC
ratio of maximum drug concentration to the MIC
AUC/MIC
ratio of the area under the concentration time curve to the MIC
time > MIC
duration of time drug concentration is above the MIC
MIC
minimum inhibitory concentration
- lowest concentration of an antimicrobial that will inhibit growth of a microorganism
concentration dependent
abx eradicate bacteria the best by achieving high concentrations at the site of infection
- Peak/MIC
- best response when concentration is >10 above the MIC
Time dependent
abx eradicate bacteria best when the time that the drug remains about the MIC is >50% of the dosing interval
