Antibiotics Basic Info Flashcards
Prophylaxis
Preventive treatment for a disease and health maintenance. Only use ABX in this situation when absolutely necessary because it can result in resistance
Empiric therapy
Therapy based on experience that begins based on educated guess in the absence of complete or perfect info
Definitive therapy
Therapy that is accepted as a specific cure for a disease
Normal flora
Bacteria that are found in the bodies normally that don’t typically cause disease unless a decrease in the immune system occurs. Most normal flora are found on the skin and in the gut
Colonization
Large scale migration or spread of a bacteria in a certain area of the body that DOES NOT make you sick
Infection
Is a spread of the bacteria that results in sickness and signs and symptoms like pus, fever, high WBC
Superinfection
An infection occurring after or on top of an earlier infection, especially following broad-spectrum ABX.
Contamination
Presence of any unwanted organism in the body
Bactericidal
Drugs that actually kill the invading organism
Bacteriostatic
These are drugs that inhibit the growth and replication of an organism
How do you select a drug in an empircial state
Collect data regarding 1. site of infection 2. recent travel hx 3. is it gram+/- 4.
What is meant by susceptibility of an organism
Once the organism is know, must pick an ABX that is most specific in treating that bacteria
MIC
Minimum inhibitory concentration. This is the lowest concentration of the drug that results in 99.9% decline in colony count after 24hrs (inhibits growth)
MBC
Minimum bactericidal concentration. This is the minimum amount of ABX that kills the bacteria under investigation by up to 99.9%
What are two ways of determining antimicrobial susceptibility of the infecting organism
- MIC
2. MBC
Susceptible
Means the organism is responsive to the drug at the recommended dosage
Moderately susceptible
Means the organism is responsive to the drug at much higher doses (or the drug is concentrated in a specific area of treatment
Resistant
Means the organism is not expected to respond to the ABX regardless of the dose or location of delivery.
Intermediate susceptibility
Similar to moderately susceptible, but is more of a buffer between susceptible and resistant
Why is site of infection important
Because it changes what type of drug will be administered
How do most drugs get to site of infection
Through slit junctions in the tissue walls
What does the blood brain barrier do
Blocks many substances because of the single layer of endothelial cells that are fused by tight junctions.
What types of molecules can pass into the BBB
Very small lipophilic drugs and ones that are unbound to plasma proteins
What is an example of a drug that passes easily into the CNS
Chloramphenicol, because they are lipophilic
What drugs have poor CNS penetration
B-lactam
Name patient characteristics that affect the selection of an ABX
- Immune system
- Kidney/liver function
- Poor perfusion
- Age
- Pregnancy
- Lactation
What effect does immunocompromised have on ABX administration
Can result in more infection and/or the necessity for longer periods of drug administration
What would happen in a pt with poor kidney function when given ABX
May result in a build up of the drug (note—the # of nephrons decreases with age!)
What effect does poor perfusion have when administering ABX
Reduces the amount of ABX that reaches the infected area. Ex: diabetic patients with leg ulcerations
What drug is not give to pregnant women
Tetracycline - causes decrease in bone growth in children
How are drugs categorized with pregnant women
A, B, C, D, X
Category A
no risk to fetus
Category B
Animal studies do not indicate risk, but no human studies
Category C
Shows effects in animals, no studies in women
Category D
Postive evidence of human fetal risk exists, but if benefits outweigh the risk may be necessary
Category X
Extreme animal and human fetal risk, risk outweighs the benefit
What are the spectrum of activity
Narrow, extended, broad, bactericidal, bacteriostatic
Narrow spectrum
Act on a single or limited group of organisms (isoniazid)
Extended spectrum
Drugs are effective against gram + and a fair amount of gram - (ampicillin)
Broad spectrum
Works on many different organisms. Gram +/-, spirochetes, mycoplasma, chlamydia. (tetracycline and chloramphenicol)
What is the preferred route of ABX administration
Oral, unless it is something like vancomycin that is poorly absorbed
What is rational dosing based on
The kinetics and dynamics of the ABX
What are the 3 properties that have significant influence on dosing frequency
- Concentration dependent killing
- Time dependent killin
- Postantibiotic effect
Concentration dependent killing
Drugs that show a significant increase in the rate of bacteria killing. As concentration increases, so does organism death (aminoglycocides) - bolus dosing
Time dependent killing
Drugs that have blood concentrations above the MIC for a good % of time. Usually done as a continues dosing schedule
What is meant by synergism
Means that two ABX can be given to a pt and the combo is more effective than treatment with just an individual drug
Why is it better to treat with just one ABX
- Reduces resistance
- Reduces possibility of superinfection
- Minimizes toxicity
What is an example of a combo ABX administration
Amoxicillin and clavulanic acid (Amox stops the growth of the bacteria, clavulanic acid prevents the bacteria from destroying or resisting amox). Often used in treatment of TB
When is it good to use combo treatments
When the synergistic effects are good and possibly when the infection is of unknown origin
What happens if a patient is taking an ABX that inhibits CYP450
It may have an adverse effect on another drug in the system. Meaning, if the patient is taking both an ABX and something else, and one drug blocks the metabolism action (CYP450), then you end up with a higher concentration of drug than would be wanted.
What does CYP450 do
Metabolizes drugs
What are two examples of CYP450 inhibiting ABX
Ciproflaxacin and erythromycin
What is cross resistance (sensitivity)
Means that if the bacteria is resistant to a certain drug, it may also be resistant to other drugs that share the same MOA.
What percent of people have a cross sensitivity of penicillin and cephalosporins
8-10&
