Antibiotics Flashcards
1
Q
Penicillins
A
- Bind to penicillin binding proteins (PBPs) and inhibit transpeptidase rxn and cross-linking of peptidoglycans
- Enters inflamed meninges
- Can produce hypersensitivity rxns: hives, SOB, anaphylactic shock (severe), and skin rash (mild)
- Other adverse effects: diarrhea, superinfections
- Penicillins (ampicillin), cephalosporins, or vancomycin with aminoglycoside (gentamicin): synergistic effect that enhances bactericidal functions
- Ampicillin/cephalosporin or vancomycin makes pores in the bacterial cell wall through which amino glycosides can enter the bacteria
- Aminoglycoside dose is decreased to minimize its toxicity
2
Q
Narrow spectrum penicillins
A
- Penicillin G (IM or IV). Effective against strep and meningococci. Not effective against staph, pneumococci or gonococci
- Mostly effective against GP bacteria (outer membrane limits entry of drug in GN)
3
Q
Penicillinase resistant
A
- Nafcillin (oral/PA, biliary excretion) and dicloxacillin (oral): only for GP (bulky hydrophobic group cannot pass through porin), used to treat strains of staph that express penicillinase
- Treats endocarditis, osteomyelitis, and cellulitis
- Staph resistant to these are MRSA (methicillin-resistant)
4
Q
Aminopenicillins
A
- Amoxicillin (oral) and ampicillin (oral/PA, biliary excretion): can be used to treat both GP and GN
- Amoxicillin: is the drug choice to treat otitis media, may be combined w/ penicillinase inhibitor (clavulanate)
- Ampicillin: treats meningitis and other infections from listeria, may be combined w/ penicillinase inhibitor (sulbactam)
5
Q
Cephalosporins
A
- Inhibit cross-linking of peptidoglycan by binding to PBPs
- Low cross-rxn w/ penicillin allergies (severe penicillin allergies may elicit some run to cephalosporins)
- Penicillins (ampicillin), cephalosporins, or vancomycin with aminoglycoside (gentamicin): synergistic effect that enhances bactericidal functions
- Ampicillin/cephalosporin or vancomycin makes pores in the bacterial cell wall through which amino glycosides can enter the bacteria
- Aminoglycoside dose is decreased to minimize its toxicity
6
Q
1st generation cephalosporins
A
- Effective against GP cocci
- Cefazolin (IV): surgical prophylaxis against staph
7
Q
2nd generation cephalosporins
A
- Effective against both GP cocci and GN bacilli
- Cefprozil (oral): treats otitis media from H influenzae (resistant to amoxicillin), also community acquired pneumonia
8
Q
3rd generation cephalosporins
A
- Effective against GN bacilli
- Ceftriaxone (PA, biliary excretion) and cefotaxime (PA): both are used to treat meningitis
- Ceftriaxone is drug of choice for gonorrhea
9
Q
Vancomycin
A
- Irreversibly binds to peptidoglycan precursor (not to PBP), not a beta-lactam and is resistant to penicillinase. GP bacteria only
- Given via slow IV infusion, can cause red man syndrome (infusion-related toxicity due to histamine release)
- Enters inflamed meninges
- Can enhance nephrotoxicity of other drugs, can cause ototoxicity at high levels
- Used to treat patients w/ penicillin allergies, MRSA patients w/ medical devices, enterococcal endocarditis
- Pseudomembraneous colitis from C difficile
10
Q
Aminoglycosides
A
- Binds to 30S subunit and interferes w/ initiation of proteins synthesis. Also causes misreading of genetic code. Results in post-antibio effect
- Not orally absorbed, does not enter CSF, dose is adjusted based on creatinine clearance
- Once daily dose to minimize renal toxicity
- Includes gentamicin and neomycin
- Gentamicin used against enterococcal and staph infections
11
Q
Side effects and drug interactions of aminoglycosides
A
- Can cause renal toxicity and ototoxicity, both cochlear toxicity (irreversible) and vestibular toxicity (reversible)
- Penicillins (ampicillin), cephalosporins, or vancomycin with aminoglycoside (gentamicin): synergistic effect that enhances bactericidal functions
- Ampicillin/cephalosporin or vancomycin makes pores in the bacterial cell wall through which amino glycosides can enter the bacteria
- Aminoglycoside dose is decreased to minimize its toxicity
12
Q
Tetracyclines
A
- Blocks tRNA binding to 30S subunit, preventing addition of new AA
- Bind to calcifying teeth and bones (mostly in children, pregnant and nursing mothers, stunts growth and discolors teeth), absorption is decreased if metal products are ingested (dairy, antacids)
- Cause hepatitis in pregnant women
- Cause nephrotoxicity and photoxicity
13
Q
Tetracycline drugs
A
- Tetracycline and doxycycline (biliary excretion): broad spectrum bacteriostatic
- Used to treat rickettsia (rocky mountain spotted fever), lyme disease (borrelia burgdurferi), chlamydia trachomatis, shorten cholera therapy, acne
14
Q
Macrolides
A
- Bind to 50S subunit and prevents translocation of peptide from A to P site (blocks peptidyl transferase)
- Does not enter CSF, can cause ototoxicity at high doses
- Erythromycin can cause epigastric distress, cholestatic jaundice
- Erythromycin inhibits Cyp450, which metabolizes cyclosporin (CSA) and warfarin, leading to increased plasma levels of CSA and warfarin
- Causes excess immune suppression and renal toxicity of CSA
- Cause increased prothrombin time and bleeding from warfarin
- Replace erythromycin w/ azithromycin (does not inhibit CYP450), decrease warfarin/CSA doses
15
Q
Macrolide drugs
A
- Erythromycin and azithromycin (both biliary) used for therapy and prevention of pneumonia
- Also treats chlamydia pelvic infection, H influenzae otitis media
- More for GP bacteria
