Antibiotic Classes and MOA Flashcards
What are the targets for killing a cancer cell?
DNA and Mitotic tubules
Do we want to target what we do in cancer cells when trying to kill bacteria?
NO. Because bacterial cells have things in them that our cells don’t and therefore we can target that
What are some things we target in bacterial cells?
- Cell wall synthesis
- Transcription and translation
- DNA synthesis and integrity
What do bacteriostatic drugs do?
- Inhibits cell growth, does NOT kill the cell
- They slow down the spreading of the bacteria and then the immune system takes over for the rest
What do bactericidal drugs do?
Kill bacteria
What do bacteriostatic drugs target?
Protein synthesis (except aminoglycosides)
What do bactericidal drugs target?
Cell wall synthesis
Who should get bacteriostatic drugs?
- Non-immune compromised
- Uncomplicated infections
Who should get bactericidal drugs?
Immune compromised (particularly if life threatening infection)
How many drugs are bacterial infections usually treated with?
1 drug
What is antibiotic synergism and when would you use it?
- Combination therapy (using 2+ antibiotics)
- Can be critical for life-threatening infections
- Infrequently would 2 antibiotics in the same class be used together
What is the MIC?
- Minimal inhibitory concentration (minimal effective dose)
- When the curve drops below the MIC you must redose
- how much drug you need to stop the bacteria from growing
When are concentration dependent antibiotics most effective?
When they have a high peak concentration
- Highest concentration kills
- Aminoglycosides
When are time-dependent antibiotics most effective?
When there is a long exposure to a drug
- Longest duration over MIC kills
- Beta-lactams
What makes up the cell wall?
Peptidoglycan
Why is peptidoglycan a target for antibiotics?
Three enzymes are needed to build the polymer and all three are targets for antibiotics
What is peptidoglycan made of?
Two amino sugars in chain cross-linked to 5 amino acids
What are the two sugars in peptidoglycan and which has amino acids attached to it?
NAG and NAM
-NAM has the amino acids on it
How are the sugars connected?
They are cross-linked via 5 glycines and this is referred to as TRANSPEPTIDASE ENZYME
What is the target for beta lactam drugs?
Transpeptidase enzyme
What are three reasons for antibiotic resistance to penicillin?
- Bacteria developed “penicillinase enzymes”
- Bacteria have resistant transpeptidase enzymes
- Bacteria have multiple resistance patterns
What is the function of an OAT?
Secretes penicillin drugs into urine, enhancing elimination
What is probenicid?
- OAT inhibitor
- Using probenicid with penicillin helps prolong blood and tissue levels of the antibiotics, giving longer duration of efficacy
Why would you not want to give probenicid to a patient with a UTI?
Because probenicid keeps the drug away from the urine so its not excreted, but with a UTI we want the drug to go to the urine
______ have surpassed the use of oral amino and natural penicillins.
Oral Cephalosporins
What are the two most common oral cephalosporins used currently?
Cefdinir and Cefpodoxime (both are 3rd generation)
Unless a resistant organism has been previously identified, what two generations of cephalosporins can be started for broad empiric coverage?
3rd or 4th generation
What generation are common pre-op antibiotics when viscera are not entered?
1st generation
Why is it necessary to use a different beta lactam antibiotic when treating a strept throat infection vs an E. coli UTI?
Because even though all bacteria have the transpeptidase enzyme, different transpeptidase enzymes are found in different bacteria
What are processes of the cell wall we target to kill the cell?
- Transpeptidase (BLs)
- Transglycosylation (binds NAG-NAM units together)
- Transamination (binds the peptides to NAM)
What is the action of vancomycin?
Inhibits cell wall synthesis
- Blocks transglycosylase (binding of NAM and NAG)
- Blocks transpeptidase
- Bactericidal
Does vancomycin treat gram + or -?
Gram + ONLY
What route is vancomycin given?
- Poorly absorbed orally
- IV requires monitoring to prevent renal and ototoxcitiy
What are the chemical properties of vancomycin?
- Glycopeptide
- BIG molecule
- Polar
- Water soluble
What is vancomycin used for?
BIG GUN
- Only used for severe or resistant gram positive infections
- Sepsis due to strep. pneumo or MRSA
What are potential side effects of vancomycin?
- Red man syndrome
- Renal and Oto toxic (too high blood levels of vancomycin can cause dead kidneys and deafness)
Is vancomycin a concentration-dependent or time-dependent drug?
Time-dependent
- Its efficacy is primarily dependent on Duration of time above the MIC, not the Cpeak
- Too high Cpeak is toxic!!!
What drug class is daptomycin?
Lipopeptide
What is the action of daptomycin?
Toxic to the cell wall and cell membrane
- Binds to the membranes and disrupts non-polar permeability
- Bactericidal
- Won’t use unless consulted with infectious disease
What is the action of fosfomycin?
It blocks an early step in cell wall synthesis
What is fosfomycin a good choice to treat?
Uncomplicated UTI
*Beta-lactam allergies
How can we target protein synthesis in bacterial cells without it hurting our own cells?
Human ribosomes (which are responsible for protein synthesis) have 40s and 60s subunits while bacterial ribosomes have 30s and 50s ribosomes
What drug classes are protein synthesis inhibitors?
- Tetracyclines (30s bacteriostatic)
- Macrolides (50s bacteriostatic)
- Aminoglycosides (30s bactericidal)
- Lincosamides & Oxazolidinones (50s bacteriostatic)
What two drugs in the tetracycline class do we most often use?
- Doxycycline
- Minocycline
What is Tigecycline?
A new tetracycline
- Only indication is Gram + resistant organisms like MRSA
- Never use for UTI
- Restricted drug
- Not able to order this for uncomplicated cellulitis
What is the tetracycline class good for?
-Well distributed in water/urine (UTIs, urethritis)
What are tetracyclines not good for?
- Not good for CNS infections as they are too large/polar to cross into CNS (not for meningitis)
- Drugs chelate calcium which discolors teeth (don’t take with dairy products)
What is the most often used macrolide?
Azithromycin (Z-pak)
What macrolide is infrequently used?
Erythromycin because it has many drug/drug interactions
What are the common aminoglycosides that are used?
- Gentamicin
- Tobramycin
What is the action of aminoglycosides?
- Irreversible inhibitors of protein synthesis
- Moves into cells via porin channels
- Actively transported into cytoplasm
- Binds to 30s subunit of ribosome
What should you not use aminoglycosides for?
Meningitis (poor CNS penetration)
Are aminoglycosides concentration dependent or time dependent?
Concentration, higher concentration = higher kill rate
- But higher concentration enhances toxicity risk
- Blood levels and kinetics need to be obtained
- Oto and nephrotoxic (best to get patient off of these and onto less toxic drugs)
What two drugs are sulfonamides (anti folate drugs)
-Trimethoprim
-Sulfamethoxazole
(if these two are given together its bactrim)
What can you NOT use sulfonamides for?
Streptococcus
What is the most common use for sulfonamides?
UTI (e. coli)
What three drugs are fluoroquinolones?
- Ciprofloxacin
- Levofloxacin
- Moxifloxacin
What is the action of fluoroquinolones?
Inhibit bacterial topoisomerase II
What are known complications of fluoroquinolones?
Tendon rupture, skeletal muscle injury, peripheral neuropathy
What drug is a nitroimidazole?
Metronidazole
What is metronidazole good to treat?
ANAEROBES
-Pelvic, vaginal, and intra-abdominal infections (including STDs, post-operative, perforations)
