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Protein Synthesis Inhibitors Flashcards

1
Q

Name 4 mechanisms of resistance

A

Reduced drug accumulation = efflux pumps
Alteration of target = ribosome protective proteins
Metabolic pathway = change how they work
Drug inactivation = beta-lactamase (enzymes)

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2
Q

What does it mean to methicillin resistant?

A

Methicillin is an Abx that is stable to b-lactamase, so if the microorganism is resistant to methicillin it is dangerous because this is something that should normally work = MRSA

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3
Q

Why is Mycoplasma Pneumoniae resistant to penicillins and cephalosporins?

A

Because it lacks a peptidoglycan cell wall, BUT DOES NOT produce b-lactamase
Since PCNS and Cephs are peptidoglycan cell wall synthesis inhibitors, they have no effect on Mycoplasma because it lacks a peptidoglycan cell wall

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4
Q

What is a protein synthesis inhibitor?

A

A substance that stops or slows the growth or proliferation of cells by disrupting the processes that lead directly to the generation of new proteins

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5
Q

How do protein synthesis inhibitors work? Why would you use them?

A

Target the bacterial ribosome w/in the cell

Use when you cannot relay on cell wall synthesis inhibitors

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6
Q

What is the bacterial ribosome made of?

A

70S ribosome
50S large subunit
30S small subunit

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7
Q

Which Abx affect the 30S subunit

A

Buy AT 30
Aminoglycosides: gentimicin, neomycin, streptomycin
Tetracyclines: Doxycycline, Minocyclin, Tetracyclin
Spectinomycin

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8
Q

Which Abx affect the 50S subunit

A 
Macrolides: Azithromycin, Clarithromycin, Erythromycin
Ketolide: telithromycin (Ketek)
Chloramphenicol
Clindamycin - Lincomide
Quinupristin-dalfopristin (Synercid)
Mupirocin (Bactroban)
Linezolid (Zyvox)
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9
Q

Aminoglycoside MOA:

A

affinity for 30S ribosome

narrow therapeutic to toxic ratio

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10
Q

How do aminoglycosides gain entry into the cell?

A

Disrupt Mg and Ca bridges between lipopolysaccharide moieties
Transported across membrane in energy-dependent manner - inhibited by divalent cations, increased osmolality, acidic pH and an anaerobic activity

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11
Q

Are Aminoglycosides bacteriostatic or -cidal?

A

Bacteriocidal - the only protein synthesis inhibitors that are bacteriocidal

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12
Q

How are aminoglycosides often prescribed?

A

Rarely as monotherapy due to resistance

Rx with PCNs for broad empiric coverage - synergism allows AG Gm+ coverage

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13
Q

When can AGs be used for monotherapy?

A

Tularemia
Plague
Uncomplicated, Gm -, drug resistant UTIs

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14
Q

AG Mechanism of Resistance

A

AG modifying enzymes and/or alterations to ribosomal 30S binding sites
Enzymes often plasmid borne
Diminished uptake due to mutations in electrochemical gradient

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15
Q

AG Spectrum of Activity

A 
Aerobic, Gm- bacteria
Enterobacteria
Pseudomonas
Gm + staph/strep with PCN synergism
NO anaerobic coverage
Below the belt infections
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16
Q

AG PK

A

Good distribution: low protein-binding and water soluble
Does not cross BBB or bronchial secretions - dislikes low pH
Excreted virtually unchanged in urine
Given IV or IM

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17
Q

AG clinical indications

A

external otitis media - topical (pseudomas)
chronic pulm infx in CF - inhaled tobramycin
Gm - bacillary meningitis - intrathecal or intraventricular
Peritoneal dialysis peritonitis - intraperitoneal
Prosthetic joint infx - impregnated cement formulation

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18
Q

AG toxicity

A

Nephrotoxicity - reversible

Ototoxicity - nonreversible - tinnitus, vertigo, ataxia

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19
Q

Name the AGs -NASTG

A 
Gentamicin
Tobramycin
Neomycin
Amikacin (Amikin)
Streptomycin
NASTG
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20
Q

Name the Tetracyclines - DTMD

A 
Doxycycline
Tetracycline
Minocycline
Demeclocycline
DTMD (death to microbe demons)
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21
Q

Tetracycline MOA

A

binds to 30S subunit - bacteriostatic

blocks access of tRNA o mRNA-ribosome complex (A site), inhibiting bacterial protein synthesis

22
Q

Tetracycline SOA

A

Broad spectrum against Gm + and Gm - anaerobes
Mycoplasma, rickettsia, legionella, spirochetes, chlamydia
STI, atypical pneumonia, chronic bronchitis, acne, alternative for sinusitis and acute prostatitis

23
Q

Tetracycline Resistance

A

If resistant to one Tetracycline, will be resistant to all
Cell develops efflux pumps
Forms ribosomal protection proteins

24
Q

Tetracycline PK

A

Oral, IV, IM (not recommended)
Absorption: adequate but incomplete orally - do not take with dairy (Ca, Al, Mg, Fe will bind) - less with doxy
Distribution: concentrates in liver, kidney, spleen, skin, tissues undergoing calcification (teeth and bones)
insufficient in CNS
Crosses placental barrier

25
Tetracycline Elimination
concentrates in liver where it is metabolized and conjugated Released in bile Reabsorbed in intestine to enter urine via glom filtration Doxy exception: metabolite preferentially excreted via bile into feces = can use in renally compromised patients
26
Tetracycline AE
Teeth staining, deposits in bone causing hypoplasia and growth stunting GI discomfort with dairy - take with other food Phototoxicity Hepatotoxic Vestibular problems: dizzy, N/V with minocycline
27
Tetracycline CI
pregnant women, lactation Children < 8 Renal impairment (except doxy) Liver function impairment
28
What is doxy a DOC for?
mycoplasma pneumoniae, chlamydia, rickettsial (RMSF), and lyme Chlamydia, Q fever, bubonic plague, cat scratch fever, RMSF, lyme, PID
29
Name the macrolides - ACET
``` erythromycin azithromycin (Zithromax) clarithromycin (Biaxin) - good for bartonella (Cat Scratch Fever) Ketek - telithromycin ACET ```
30
Macrolide MOA
Binds irreversibly to 50S subunit Inhibits translocation steps of protein synthesis Bacteriostatic
31
Erythromycin SOA
``` Same as PCN - use in allergy Chlamydia, Mycoplasma, legionella Gm - and Gm+ coverage - Step p., GABHS Strep, CAP, acne Safe in pregnancy SE: poor GI tolerance ```
32
Azithromycin SOA
Less active against strep and staph than eryth Respiratory infx: H. flu, M. cat, CAP, ABECB - anti-inflam DOC Chlamydia
33
Clarithromycin SOA
Similar to erythromycin + H. flu CAP, legionella, H. pylori Sinusitis, bronchitis, ABECB
34
Macrolide Resistance
Most strains of staph are erythromycin resistant Changes to rRNA prevent macrolide binding Altered macrolide binding site on ribosomal RNA = high resistance Active macrolide efflux pumps
35
Macrolide PK (A&D)
Eryth must be enteric coated - readily absorbed Azith and Clarith = stable in stomach acid, readily absorbed Distributed well in tissues except CSF
36
Macrolide PK (M&E)
Eryth: CYP450 metabolized - concentrated in bile Clarith: metabolized by liver - COLCHICINE - eliminated by kidneys and liver (adjust in renal patients) Azith: not CYP metab, long half-life - few drug interactions Concentrated in bile
37
Macrolide AE
GI distress - especially with erythromycin QT prolongation - mainly erythromycin - get EKG Hepatotoxicity with ketek (telithromycin)
38
Chlorampheicol MOA and SOA
binds 50S subunit and inhibits protein synth at the peptidyl transferase reaction Broad SOA against anaerobes Not good for pseudomonas or chlamydia
39
Chlorampheicol PK
Completely absorbed orally | Enters CSF
40
Chlorampheicol AE
Hemolytic anemia Aplastic anemia - fatal Reversible anemia Gray baby syndrome
41
Chlorampheicol Warnings/Facts
Highly toxic - restricted to life-threatening infx with no other alternative
42
Clindamycin Class and MOA
``` Lincosamide MOA: Binds irreversibly to 50S subunit Inhibits translocation steps of protein synthesis Bacteriostatic MOA same as macrolides ```
43
Clindamycin SOA
Gm+ cocci and anaerobes (above diaphragm) Good for osteomyelitis Penetrating wounds of abdomen and gut
44
Clindamycin PK
Well absorbed orally | Distributes well except CSF
45
Clindamycin SE
C. diff leading to fatal pseudomembranous colitis | SE: diarrhea, rash, vomiting
46
What medications do you think about when treating an anerobe?
Clindamycin or Metranidazole | For gut or female genital infx
47
Linezolid (Zyvox) MOA
bind to 50S subunit to prevent formation of initiation complex for protein synthesis Bacteriostatic for staph and enterococci Bacteriocidal for strep
48
Linezolid (Zyvox) SOA
Gm+ and anaerobes MRSA, VRE, enterococcus faecium and faecalis, bad skin infx Atypicals: Chlamydia, Mycoplasma, Legionella
49
Linezolid (Zyvox) DOC for?
Vanco resistant enterococcus (VRE) | MDR TB
50
Linezolid (Zyvox) PK
No dose adjustment needed for renal, hepatic, or age | 100% oral absorption
51
Linezolid (Zyvox) SE
GI, NVD, HA, thrombocytopenia, C. diff BM suppression, neuropathy, lactic acidosis, optic neuritis Weak MAOI action: boosts dopamine, serotonin etc. Avoid ETOH, aged cheese, high tyramine food
52
Lincomycin
``` Lincosamide Rarely used except in pts with bad infx and PCN allergy SE: C. diff, BM suppression Narrow SOA: Gm+ and mycoplasma Similar to macrolides ```

ID Pharm (6 decks)

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