Antibiotic Lecture Part 1 Flashcards
Define Narrow Spectrum
Antibiotics that are only effective against a SMALL number of bacteria
Define Broad Spectrum
Effective against MANY bacteria
Give examples of both a narrow spectrum and broad spectrum antibiotic
Narrow: Penicillin
Broad: Tetracycline
Define Bactericidal:
Antibiotic has the ability to KILL bacteria
Define Bacteriostatic:
Antibiotic inhibits bacterial growth or slows the growth
What is Antibiotic Antagonism:
When 2 antibiotics are used together, one antagonizes the effect of the other
T or F, Never combine a bactericidal antibiotic with a bacteriostatic antibiotic in the same person
True
T or F, Bactericidal antibiotic will inhibit or diminish the effects of Bacteriostatic antibiotic
False, Bacteriostatic will inhibit effects of Bactericidal
If tetracycline and penicillin are given together, which will NOT be effective?
Penicillin will NOT be effective. This is because it is a bactericidal antibiotic
T or F, Not all antibiotics are bacteriostatic
False, ALL are bacteriostatic (depending on dose)
T or F, All antibiotics are bactericidal at therapeutic doses
False, NOT all
What is Minimum Inhibitory Concentration
A test used to determine bactericidal concentration of an antibiotic
T or F, Theoretically, all antibiotics are bactericidal, but the dose to achieve bactericidal effects would be so high that it would kill the patient
True
Define Antibiotic Synergism:
Occurs when 2 antibiotics work together for a more positive effect when given to the same patient
What five steps are used to choose an antibiotic
- Identify the microorganism
- Determine the most effective antibiotic against that organism
- Choose an antibiotic with low host toxicity
- Choose a bactericidal antibiotic
- Choose an antibiotic with low resistance potential
Is it a good thing to try and identify the microorganism in the mouth?
Not really efficient clinically, in normal healthy ambulatory population, the predominant microorganism in the oral cavity is going to be gram positive strep or staph. 90-95% of the time. Without even taking a culture, we know that the oral infection is most likely a gram positive strep or staph
What is the most effective antibiotic against gram positive strep or staph?
Penicillin
What is the least toxic antibiotic
Penicillin
- Cannot kill the host at ANY concentration
T or F, 10% of the population is allergic to penicillin but it is not toxic to them.
True
Why do we try to choose a bactericidal antibiotic?
If a patient has an infection, it drains their resistance and disability to fight off other infections. An antibiotic kills bacteria so we don’t have to rely on the patient’s defense mechanisms.
When choosing antibiotic with low resistance potential, what are 4 ways that we minimize resistance:
- Give an adequate dose
- Take for an adequate duration
- Avoid repeated administration
- Avoid topical administration
T or F, Is it ok to give patients a lower dose of antibiotics just in case they are allergic to prevent the patient from going into anaphylactic shock
False, Remember that allergic reactions are NOT dose dependent
T or F, Do not give patients same antibiotic week after week
True, Bacteria develop mechanisms to become resistant
Sulfa Drugs are indicated for what use?
Used primarily for urinary tract infections (UTI)
- No indications for use in dentistry
What was the first antibacterial agent?
Sulfanilamide
Mechanism of action of penicillins
Blocks bacterial cell wall synthesis by interfering with structural glycopeptides
- Bacterial cell death results from lysis
What is penicillinase?
Is a beta lactamase that breaks down the beta lactic ring of the penicillin molecule. Without an intact beta lactic ring, penicillin is ineffective: drug cannot inhibit bacterial cell wall synthesis
T or F, 99% of the normal, healthy ambulatory population does not have penicillinase-producing microorganisms
True
How are natural pencillins (penicillin G) administered?
Given parenterally
- They are incomplete and variable due to destruction by gastric juices when given orally
How are semi-synthetic (penicillin V) administered?
Orally
- More acid stable, therefor more uniform absorption
How much of an oral dose of penicillin is secreted within the first 4 hours?
70% of an oral dose
T or F, Penicillin molecule excreted unchanged?
True
How much of penicillin is excreted from the body via active transport?
90%
-10% passive transport
What is probenecid?
A medication used to treat gout
- Also called Benemid
How is probenecid used with penicillin?
It is used to slow the excretion of penicillin. It competes with the penicillin molecule for the active transport mechanism. probenecid has a greater affinity for the carrier than penicillin does. So if probenecid is given before penicillin is given, the penicillin is not excreted as rapidly
probenecid elevates the blood level of penicillin how much?
3-4 times; prolongs the effect of the penicillin
What are the two indications of Penicillins?
- Orofacial infections - penicillin is drug of choice
2. Prophylactic use - prevention of bacterial endocarditis and of infections around prosthetic joints and devices
What was the first penicillin produced?
Penicillin G
- Only natural penicillin available commercially
Narrow spectrum
What is the indication of penicillin G
in Treatment of STDs
What is the advantage of Procaine Penicillin G = repository form
The penicillin escapes at a slower rate out of the oil after injection
It is released over a 12-24 hour period
What is the indication for Procaine penicillin G = respiratory form
- Infections with Treponema palladium
- Anthrax
What is the advantage of Benzathine Penicillin G = repository form
Produces therapeutic blood levels that last for 3 weeks.
- Doesn’t reach the peak level that is obtained with the aqueous form of penicillin G
What is the brand name for Benzathine Penicillin G?
Bicillin
Primary indication for Bicilin or Benzathine penicillin G?
STDs
What was the first semi-synthetic penicillin
Penicillin V
Sodium penicillin V is an improved version of penicillin G why?
Because it is acid stabile
- It can be taken orally
How is Penicillin V best bioavailable?
It was first combined with sodium but later was determined that it has better bioavailability when it was in the potassium form
- Now, all forms of penicillin V are going to be in potassium form
T or F, Never write a prescription for penicillin VK
True, Just write it for penicillin V
- If you write the prescription for penicillin VK, the pharmacist has to fill the prescription with that brand name drug
Penicillin V: Bactericidal or Bacteriostatic Broad spectrum or Narrow spectrum Acid stabile or incomplete Penicillinase labile?
- Bactericidal
- Narrow spectrum
- Acid stabile
- Penicillinase labile
T or F, CDC says that when you are treating an infection, you must use the most broad spectrum antibiotic so that all bacteria will be killed
False, Narrow spectrum that is available for that particular infection
When are penicillinase-resistant penicillins used?
Only used if the patient has an infection caused by penicillinase-resistant microorganisms
What 4 reasons must you consider in not using penicillinase-resistant drugs
- Promotes resistant microorganisms
- More expensive
- More toxic
- Not as effective as penicillin V
