Principles of Antimicrobial Therapy Flashcards
When selecting an antimicrobial, what are the 4 principles you must consider?
- Confirm presence of infection
- Identify pathogen
- Select presumptive therapy
- Monitor therapeutic response
Drug Action and Mechanism is considered to be (pharmacodynamics/pharmacokinetics)
Pharmacodynamics
Absorption, Distribution, Metabolism, Excretion is considered to be (pharacodynamics/pharmacokinetics)
Pharmacokinetics
What does the body do to the drugs?
Affects serum + tissue levels
What reactions occur in phase I metabolism?
Dealkylation, hydroxylation, oxidation, deamination
What enzyme system does phase I metabolism occur in?
Cytochrome P-450
What does phase I metabolism do exactly?
Inactivates substrate into a more polar compound
What reactions occur in phase II metabolism?
Glucuronidation, sulfation, acetylation, conjugation
What does phase II metabolism do exactly?
- Conjugates parent compound with larger molecule to increase polarity
- Inactivates parent compound, renally excreted
What is distribution of a drug affected by?
- Lipophilicity
- Partition coefficient
- Blood flow to tissues
- pH
- Protein binding
What is bioavailability?
Amount of drug that reaches systemic circulation
Glomerular filtration, tubular secretion, passive diffusion + dialysis is considered (renal/non-renal) clearance
renal
Sum of clearance pathways not involving the kidneys is considered (renal/non-renal) clearance
non-renal
Steady state concentrations reaches after _____ half lives
4 to 5
Half-life is affected by changes where?
End-organ function & protein binding
How do you find total body clearance?
Renal + Non-renal clearance
(Bacteriostatic/Bactericidal) inhibits growth or replication
Bacteriostatic
(Bacteriostatic/Bactericidal) causes cell death
Bactercidal
Pharmacokinetics
Concentration vs time
Effect vs time
Effect vs concentration
Concentration vs time
Pharmacodynamics
Effect vs concentration
Concentration vs time
Effect vs time
Effect vs concentration
PK/PD
Effect vs time
Concentration vs time
Effect vs concentration
Effect vs time
What is the therapeutic index?
Ratio between toxic and effective dose that shows the normal range of pharmacological effect
What is the therapeutic window?
Area between low efficacy and high efficacy of the ED50
Where drug concentrations should be maintained for adequate therapeutic effect
What is post antibiotic effect?
Delayed regrowth of bacteria following exposure to antimicrobial
If you’re allergic to penicillin, what else should you avoid?
Cephalosporin + Carbapenems
Can antimicrobials cross the placenta?
Yes
Which antibiotics appear to be safe in pregnancy?
- Penicillins
- Cephalosporins
- Erythromycin
What are some effects of being pregnant + having antibiotics?
- Fetus at risk for teratogenicity
2. Some AB are cleared more rapidly
What genetic/metabolic abnormalities should you look out for when taking AB?
G6PD deficiency, risk of increased RBC hemolysis
What is the most important factor to consider in antimicrobial selection?
Site of infection
Is toxicity a concern for using a combination antimicrobial?
Yes, but can also benefit pt by decreasing toxicity
How much evidence is there for using combination antimicrobials?
Theres just weak supporting evidence
What kind of effect can you predict from using antimicrobials?
Synergistic, Antagonistic, or no change at all
Whats an example of an antagonistic combination therapy?
Using bacteriostatic + bactericidal
Tetracycline inhibits growth, but penicillin requires bacteria to grow in order to be effective
Whats an example of a synergistic combination therapy?
Using bactericidal and another bactericidal
Penicillin + aminoglycoside combination work together great
What should you monitor when you use antimicrobials?
Efficacy + toxicity
