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Flashcards in Antibiotics Deck (22):
1

Penicillins

-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

Narrow spectrum penicillins

-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

Penicillinase resistant

-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

Aminopenicillins

-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

Cephalosporins

-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

1st generation cephalosporins

-Effective against GP cocci
-Cefazolin (IV): surgical prophylaxis against staph

7

2nd generation cephalosporins

-Effective against both GP cocci and GN bacilli
-Cefprozil (oral): treats otitis media from H influenzae (resistant to amoxicillin), also community acquired pneumonia

8

3rd generation cephalosporins

-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

Vancomycin

-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

Aminoglycosides

-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

Side effects and drug interactions of aminoglycosides

-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

Tetracyclines

-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

Tetracycline drugs

-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

Macrolides

-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

Macrolide drugs

-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

16

Sulfonamides

-Inhibit dihydropteroate synthesis, decreasing folic acid
-Acetylated forms excreted in urine, can cause crystalluria
-Displaces other drugs from albumin (class II). This causes class I drugs (methotrexate, warfarin) to be displaced from albumin and increased their plasma levels (reduce dose of class I drug)
-Also inhibits Cyp450 when used w/ trimethoprim (TMP-SMX), preventing metabolism of warfarin/CSA
-TMP-SMX not given to neonates, pregnant women, nursing women (displaces bilirubin form albumin and causes kernicterus)
-Also causes skin rashes/stevens-johnson syndrome (hypersensitivity rxn)

17

Sulfonamide drug

-Sulfamethoxazole (SMX): used to treat UTI

18

Fluoroquinolones

-Inhibits DNA gyrase, preventing replication
-Chelates metals, long half lives, post antibio effect
-Once a day oral administration
-Can cause CNS problems at high doses or w/ coffee (inhibits CYP1A, which metabolizes caffeine)
-Can cause photo toxicity, arthropathy in children (not given to children under 18 or pregnant/nursing mothers)

19

Fluoroquinolone drugs

-Ciprofloxacin, levofloxacin: broad-spectrum, treats UTI, prostatitis, traveller's diarrhea
-Levofloxacin treats pneumonia

20

Isoniazid

-Inhibits synthesis of mycolic acid
-Acetylation inactivates it, dose is reduced in liver disease
-Can cause hepatitis necrosis (increased in elderly and alcoholics), peripheral neuropathy
-Enters CSF
-Induces Cyp450, increasing metabolism of warfarin, CSA
-First line defense against TB (Tx is: Rifampin, Isoniazid, pyrazinamide, ethambutol, or RIPE)

21

Rifampin

-Binds to beta-subunit of RNA polymerase and inhibits transcription
-Deacetylation retains activity but enhances biliary excretion
-Induces Cyp450, increasing metabolism of warfarin, CSA
-Can cause hepatitis necrosis (increased in elderly and alcoholics)
-Can cause discoloration of bodily fluids
-Treats TB (Tx is: Rifampin, Isoniazid, pyrazinamide, ethambutol, or RIPE)

22

Ethambutol

-Blocks arabinosyl transferases involved in cell wall synthesis
-Can cause acute gout, and optic neuritis (cannot discriminate red/green)
-Treats TB (Tx is: Rifampin, Isoniazid, pyrazinamide, ethambutol, or RIPE)