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KG - Pharmacology > Aminoglycosides & Broad Spectrum Antibiotics > Flashcards

Aminoglycosides & Broad Spectrum Antibiotics Flashcards

1
Q

mechanism of aminoglycosides?

A
  • targets protein synthesis (targets 30S) - irreversibly inhibits protein synthesis of susceptible microorganisms by inhibiting functioning of 30S subunit
  • blocks initiation of translation and causes the misreading of mRNA
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2
Q

“All aminoglycosides are usually used ________”

A

“All amino glycosides are usually used IN COMBINATION.”

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3
Q

list of aminoglycosides

A
  • streptomycin - TB second line agent (now more first line), IV/IM
  • gentamycin - G-, combo - IV/IM, topical
  • tobramycin - G-, combo - IV/IM, topical
  • amikacin - G-, combo - IV/IM
  • neomycin - oral, topical
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4
Q

characteristics of aminoglycosides

A
  • contain amino sugars in glycosidic linkage
  • polycations
  • POLARITY RESPONSIBLE FOR PHARMOKINETIC PROPERTIES
  • BACTERICIDAL (used in combo w/ PCN)
  • to be effective must be transported into susceptible bacteria (req O2) and bind to 30S subunit to produce non-functional 30S initiation complex
  • under aerobic conditions = BACTERICIDAL
  • not effective in anaerobes
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5
Q

when are aminoglycosides used?

A

to treat infection caused by susceptible AEROBIC G- ENTERIC BACTERIA (rods) (usu combined w/ beta-lactam antibiotics), or when suspicion of SEPSIS or ENDOCARDITIS

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6
Q

when is streptomycin used?

A
  • tularemia (francisella tularensis)
  • bubonic plague (yersinia pestis)
  • TB
  • endocarditis when w/ other agents in combo therapy
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7
Q

when is gentamycin/tobramycin/emikacin used?

A

against P. aeruginosa

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8
Q

when is neomycin/gentamycin used?

A

topical application of wounds & burns caused by gram neg organisms

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9
Q

What is the recommendation for infections due to Enterococci?

A
  • two synergistic antibiotics

- rec therapy = gentamycin or streptomycin + vancomycin or a b-lactam (such as PCN)

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10
Q

DOC for Gram + cocci (enterococci species)?

A

aminoglycoside + PCN

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11
Q

DOC for tularemia? (rabbit fever)

A

gentamycin

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12
Q

DOC for pseudomonas aeruginosa?

A

aminoglycoside + antipseudomonal PCN

tobramycin + piperacillin/ticarcillin

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13
Q

amino glycosides are CONCENTRATION DEPENDENT KILLING. what does this mean?

A

increasing concentrations kill an increasing population of bacteria and at a more rapid rate

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14
Q

aminoglycosides have a significant POST-ANTIBIOTIC EFFECT - explain

A
  • antibacterial activity persists beyond time that antibiotic is measurable
  • single large dose has better efficacy than multiple smaller doses - reduces toxic side effects
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15
Q

toxicity of aminoglycosides

A
  • OTOTOXICITY
  • NEPHROTOXICITY
  • overgrowth of non-susceptible organism
  • GI upset
  • neuromuscular weakness
  • nausea, vomiting
  • allergy
  • diarrhea
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16
Q

toxicity of loop diuretics (ethacrynic acid, furosemide)? (usu given at same time as aminoglycoside)

A
  • OTOTOXICITY
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17
Q

toxicity of vancomycin, cephalosporins, cisplatin, cidofovir?

A
  • NEPHROTOXICITY
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18
Q

pharmokinetics of aminoglycosides

A
  • IM or IV or topical
  • none absorbed adequately after oral admin (not absorbed through GI tract; 3% for neomycin)
  • none penetrates CSF readily
  • normal kidney rapidly excretes all
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19
Q

mechanism of action chloramphenicol

A

reversibly binds to 50S subunit of bacterial 70S ribosomes and prevents attachment of amino acid containing end of aminoacyl-tRNA to acceptor sire on ribosome

  • inhibits protein synthesis
  • BACTERIOSTATIC
  • can be bactericidal against H.flu, Neisseria mening, strep pneu at therapeutic concentrations
  • can INHIBIT MITOCHONDRIAL PROTEIN SYNTHESIS IN MAMMALIAN CELLS
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19
Q

resistance of aminoglycosides?

A
  • deficiency of ribosomal receptors (if it can’t bind, can’t have effect)
  • lack of permeability of drug molecule into bacteria
  • enzymatic modification by bacteria

*** aminoglycosides usu used in COMBO w/ other antibiotics

20
Q

3 classes of BROAD SPECTRUM ANTIBIOTICS?

A
  • chloramphenicol
  • tetracyclines
  • glycylcyclines
20
Q

characteristics CHLORAMPHENICOL (chloromycetin)

A
  • broad spectrum
  • first/prob only successful synthetic antibiotic
  • associated w/ FATAL APLASTIC ANEMIA and other serious/fatal side effects (used when no other options available)
21
Q

toxicities of chloramphenicol

A
  • dose dependent (bone marrow suppression) - anemia, leukopenia, thrombocytopenia, reversible upon discontinuation of drug
  • dose independent (fatal aplastic anemia = rare)
  • GRAY BABY SYNDROME in infants - inadequate activity of glucoronyl transferase in newborn liver
  • rash, angioedema, urticaria
  • rarely anaphylactic rxns
21
Q

chloramphenicol resistance

A
  • acetyl transferase acetylates and inactivates chloramphenicol
  • efflux pumps
22
Q

when is chloramphenicol used? (for life threatening infections)

A
  • typhoid fever
  • meningitis (H.flu [bactericidal], N. meningitidis [PCN resistant], S. pnuem.)
  • rickettsia, brucellosis, rocky mountain spotted fever, melioidosis
  • bacterial conjunctivitis (topical)
22
Q

pharmokinetics of chloramphenicol

A
  • parenteral admin
  • best CNS penetration
  • metabolized in liver (90%), CONJUGATED w/ GLUCURONIC acid to form chloramphenicol glucoronate - inactive metabolite
  • metabolite excreted in kidney
23
Q

list of tetracyclines

A
  • TETRACYCLINE (sumycin) - oral, topical
  • doxycycline (vibramycin) - oral
  • minocycline (minocin) - oral
24
Q

mechanism of action of tetracyclines

A
  • inhibition of bacterial protein synthesis
  • bacteriostatic
  • bind reversibly to 30S ribosomes, prevent access of aminoacyl tRNA to receptor site on mRNA complex
  • this prevents acids to growing peptide chain
25
Q

spectrum of tetracyclines

A
  • G-
  • G+
  • anaerobes
  • aerobes
  • atypicals
26
Q

organisms related to tetracyclines?

A
  • B. fragilis
  • proteus (most strains)
  • pseudomonas (most strains)
27
Q

treatment for H. pylori?

A

tetracyclines w/ metronidazol & bismuth

28
Q

treatment for cholera?

A

DOC = tetracyclines (doxycycline)

29
Q

treatment for mycoplasma pneumonia?

A
  • DOC = tetracyclines

- erythromycin

30
Q

treatment for infections w/ chlamydia?

A
  • DOC = tetracyclines

- azithr/erythromcin

31
Q

treatment for rickettsial infection/RMSF?

A
  • DOC = tetracyclines

- doxycycline for RMSF

31
Q

treatment for Vibrio species?

A

DOC = tetracyclines

32
Q

treatment for brucellosis?

A

tetracyclines

32
Q

treatment for lyme disease?

A

early - DOC = tetracyclines (doxycycline)

33
Q

treatment for plague?

A

tetracyclines in combo w/ aminoglycosides

34
Q

contraindications of tetracyclines?

A
  • pregnant women
  • children < 8 yo
  • breastfeeding women
35
Q

resistance to tetracyclines

A
  • usu conferred by efflux pumps

- resistant strains may be susceptible to doxycycline, minocycline, tigecycline - all poor substrates for efflux pumps

36
Q

pharmokinetics of tetracyclines

A
  • absorption after ORAL use adequate but incomplete (D & M better)
  • chelation w/ Ca++, Fe++, Al+++ (D & M better)
  • distribution in all tissues except CNS & joints
  • tetracyclines DEPOSIT THEMSELVES IN BONE/TEETH (chelate Ca2+
  • metabolized by liver and excreted in urine & bile
  • ## doxycycline not hepatic ally metabolized, major route excretion via FECES
37
Q

adverse reactions to tetracyclines

A
  • GI upset (from incomplete absorption)
  • NORMAL FLORA CHANGES
  • bone and teeth
  • liver damage
  • Fanconi syndrome
  • photosensitivity
  • hypersensitivity uncommon
38
Q

contraindications of tetracyclines?

A
  • pregnant women
  • children < 8 yo
  • breastfeeding women
39
Q

characteristics of glycylcyclines (tigecycline/tigacil)

A
  • synthetic derivative of minocycline
  • IV admin only
  • antibiotic for complicated skin/skin structure infections and intra-abdominal infections
  • bind to 30S ribosomal subunit
  • BACTERIOSTATIC
  • spectrum of activity of tigecycline similar to tetracycline, doxycycline, and minocycline, but shows activity against tetracycline resistant organisms
40
Q

when to use tigecycline?

A
  • activity against MRSA, MRSE, PRSP, VRE
41
Q

elimination of tigecycline?

A
  • 2/3 dose via fecal matter, 1/3 by renal excretion
42
Q

adverse effects tigecycline?

A
  • similar to tetracyclines

- main effect = nausea/vomiting

KG - Pharmacology (8 decks)

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