Antibiotics Flashcards
What are the natural penicillins and what do they treat?
PCN V (oral) and PCN G (parenteral). They treat SAC: Strep pneumoniae, Actinomyces, and Corynebacterium
What are the aminopenicillins and what do they treat?
Ampicillin (parenteral or oral) and Amoxicillin (oral)
They treat SHEL: Strep pneumo, H. flu, E. Coli, and Listeria
Combo of ampicillin/sulbactam is called? What does it treat?
Unasyn: treats community acquired pneumo, H. flu, and Moraxella
What is the only PCN you can take with meals?
Amoxicillin
Does PCN get into the meninges?
Only if the meninges are inflammed
In what organ(s) are the PCNs metabolized?
Liver & Kidney (must adjust for renal failure)
What two drugs does PCN compete with for renal excretion?
Aspirin, probeniced. If one of these drugs is in your body along with PCN, one of the drugs will “outcompete” the other for renal excretion.
What are the adverse reactions with PCN?
- Nausea/vomiting
- Hypersensitivity reactions (can be anaphylactic). Mediated via IgE and histamine release
- Pen G in high doses can be toxic to kidneys
- Diarrhea after oral dose
What is the mech of action of all the beta lactams (such as PCN, cephalosporins, and carbapenems)?
Inhibit formation of peptidoglycan cross-links in bacterial cell walls. A bacterial enzyme called beta lactamase can destroy the beta lactams and thus the bacteria can become resistant
What is the only cephalosporin on the condensed drug list?
Ceftriaxone
What are the 3 characteristics that make cephalosporins (Ceftriaxone) better than PCN?
- Broader
- Less hypersensitivity
- Less problems with bugs becoming resistant
What might you combine Ceftriaxone with to treat a nursing home patient with pneumonia?
Combine Ceftriaxone with an AMG (amikacin, gentamicin). You are treating P. aeruginosa (the most common nosocomial cause of pneumonia)
Can you take Ceftriaxone as a prophylactic?
Hell no! It is too powerful for that shit!
Ceftriaxone can also treat bacterial infection of what other “organ”? …think a red liquid..
Bacteremias! Bacterial infections in blood
Ceftriaxone is a champion at treating bacterial meningitis, why?
It crosses the BBB easily and gets into the CSF
How is Ceftriaxone excreted?
Kidneys (dose must be adjusted for renal failure)
What are 3 adverse reactions with Ceftriaxone?
- Nephrotoxic at high doses
- Severe pain with IM injections
- Hypersensitivity (but not as bad as PCN and rarely anaphylactic)
What beta lactam group has the highest of resistance to bacterial resistance?
The carbapenems
This carbapenem is commonly combined with cilastatin, a dehydropeptidase inhibitor
Imipenem
What is a major ADE of Imipenem?
Seizures
How is Meropenem different that Imipenem? (3 ways)
- You dont have to combine it with cilastatin
- Less seizures
- Less activity against Gram + cocci (S. aureus)
What is the MOA of the macrolides? Also, list the macrolides that are on the consolidated drug list
Erythromycin and Clarithromycin. MOA: bind to 50S ribosomal subunit
Are the macrolides bacteriostatic or bactericidal?
Erythromycin is bacteriostatic ONLY! Clarithromycin can be bacteriocidal at high doses
How do drugs generate resistance to Erythromycin?
The Erm gene methylates the 50S subunit thereby altering the drug’s target. This is the MLSB phenotype
What 3 places (organs or cells) does Erythromycin concentrate?
- Prostatic fluid
- Liver (check LFT’s)
- Macrophages
How are the macrolides excreted?
Bile/feces
Possible ADE’s of macrolides?
It is a CYP3A inhibitor. Can lead to heart problems like torsades de pointes, arrhythmias, prolonged QT interval (along with FQ’s and first generation anti-histamines), and sudden death
What is the main reason you would use a macrolide?
If your patient has a PCN allergy
Does charithromycin absorption decrease or increase with food?
Increases
Clarithromycin is eliminated by what organs?
Liver, kidneys (must adjust dose for renal failure)
Are the potentially severe heart problem side effects of clarithromycin as bad as erythromycin?
No, they’re not as bad.
List the fluoroquinolones (FQ’s) and their mech of action
Levofloxacin, Moxifloxacin. MOA: inhibits bacterial DNA gyrase –> bacteriocidal
How does a bacteria go about generating resistance against FQ’s?
A bacterial mutation of its DNA gyrase, specifically at the QRDR moiety.
You can combine a carbapenem and an AMG (amikacin) to treat what highly resistant bacteria?
Acinetobacter
What might inhibit the absorption of the FQ’s?
Antacids like Al, Mg, Fe, and Zn
Do the FQ’s get in the CSF?
No
Where are the FQ’s excreted?
Via bile and kidneys (must adjust for renal failure)
What 2 bugs are the FQ’s particularly good at treating?
Strep pneumo and S. aureus
What are the ADE’s of the FQs?
- QT
- NSAID seizures
- Photosensitivity
What drug can you combine with FQ to treat highly resistant Gram - organisms?
Beta lactam. In fact, the FQ’s are referred to as “AMG-lite” cuz you can combine them with a beta lactam and the side effects arent as bad as if you used an AMG (amikacin, gentamycin)
What is the only tetracycline on the abbreviated drug list? What is its MOA?
Doxycycline. Binds 30S ribosomal subunit of bacteria. Bacteriostatic
What may inhibit the absorption of doxy?
Milk and antacids
Where does doxy like to distribute?
Bones & teeth (be careful giving this drug to kids!!)
Metabolism of doxy?
Enterohepatic cycling
Excretion of doxy?
Bile only, you dont have to worry about renal function!!
What would a patient have if you were to treat them with doxy?
Atypical pneumonia
ADE of doxy?
- Photosensitivity
2. Alters gut normal flora –> Candidiasis of GI tract
