GI: Antimicrobial & Antihelminthics Flashcards
how are antimicrobials usually grouped?
- by their MOA (MC**)
- also….by their spectrum of activity (narrow or broad or gram+ or gram-)
parenteral
anything NOT PO
factors involved in picking the appropriate antimicrobial agent? (5)
- ID organism
- Susceptibility to antimicrobials (what is organism susceptible to?)
- site of action/infection
- patient factors
- cost
how to identify the pathogenic organism?
(3)
pros/cons for each
- Gram Stain–
* PROS: quick and tells you info about presence of an organism in sterile sites aka where it does not belong..SOME sense of what it is but not EXACTLY what organism is
* CONS: does not tell you exact organism - PCR–amplification of DNA/RNA fragments
* PROS: ID exact bacteria
* CONS: longer time wait - MALDI-TOF: matrix-assisted laser desorption/ionization time of flight mass spectrometry–*PROS: accurate, rapid, and cost effective
what is the gold standard for identifying an organism?
CULTURES
**but they take a while to get results….. so we do rapid tests tooo
do you get culture before or after initiating antimicrobial tx?
BEFORE
what are some exceptions to starting ABX therapy before culture results
*severely ill patients
*hypotensive
*high fever
basically SEPTIC PATIENTS–bacteremia
define: empiric antimicrobial treatment
* why do we use it?
* what kind of antibiotic is generally used
* how do we pick abx?
TX based on the best clinical “guess” of what the offending organism is
- for scenarios where delaying treatment could result in serious harm to PT or in immunocomp–>neutropenic PTs (low WBCs),
- most common organisms that are associated with the disease process of the PT
- get cultures… THEN right away start empiric therapy
How to pick ABX:
- site of infection
- local resistance patterns EX HP
- Based on clinical scenario–did they just take a recent ABx, or are they sensitive to a specific one
**the abx we choose is more broad spectrum versus narrow
ex of bacteria that are predictable regarding susceptibility
N. meningitidis
ex of bacteria that are not so predictable regarding susceptibility
enterococcus
staphylococcus
bacteriostatic vs bactericidal
static–drugs generally inhibit bacterial browth and replication at a level of drug that can be achieved by PT– then the host does the rest of the work to kill bacteria (they target the protein synthesis)
cidal–drugs kill bacteria (>99% within 12-24 hours incubation) they target cell wall
can one agent be bacterialcidal to one microbe and bacterialcidal to another?
YES
define minimum inhibitory concentration (MIC)
*imp for?
Define Minimum bactericidal concentration (MBC)
min amt of [drug] that prevents visible growth of microbe after 24 hours
- imp for definitive treatment***
- gives us in-vitro vs in vivo information
MBC: lowest [ ] of antimicrobial agent that results in 99.9% decline in colony county after over-night broth dilution incubations
rarely determined in clinical practice bc of time and labor***
drugs are carried to tissues by?
capillaries
protected sites from abx?
brain
eyes
joints
testes
what kind of drugs easily penetrate BBB
*when can other drugs pass through BBB?
small, not protein bound (free) lipid soluble drugs**
*others can pass easily through when there is meningeal inflammation
list some patient factors we consider when picking an ABX (7)
- status of immune system– what is their WBC?
- Renal function–dose adjustment, monitering levels
- Hepatic function–metabolism of drugs
- Perfusion/absoprtion (i.e GI tract) or DM patients
- Age (elderly, newborn)
- Pregnancy–does drug cross placenta? breast milk?
- risk factors for multi-drug resistance (recent abx use, hospitalization, nursing home, immunocomp)
every single time you prescribe an abx (usually inpatient setting vs outpatient), what levels should you always know?
BUN
creatinine
AKA know their renal function!!!!!!!
which ABX is generally least toxic?
PCNs
which ABX is generally highly toxic?
Chloramphenicol
think of it like CLOROX=TOXIC
when do we give abx PO?
for mild infections
when enteral absorption not compromised
MC outpatient
when do we give abx parenteral?
- drugs poorly abs by GI tract
- severe infections–>higher serum [ ] are needed to tx
- transitioning hospitalized PT from IV to PO (before they are discharged)
dosing schedule based on?
- pharmacokinetics (MOA and effects)
- pharmdynamics (ADME)
is dose a measure of drug exposure?
why/why not
no
*drug [ ]s fluctuate in patients
