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CMBM Exam 4 > Tetracyclines/Aminoglycosides/Macrolides/Misc. > Flashcards

Tetracyclines/Aminoglycosides/Macrolides/Misc. Flashcards

1
Q

Tetracyclines

A
  • Doxycline
  • Minocycline
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2
Q

Tetracyclines MOA

A
  • Bacteriostatic, reversibly binds 30 S subunit of bacterial ribosomes, block protein synthesis
  • Blocks binding of amino-acyl tRNA
  • Passibe diffusion thru outer cell wall
  • Drugs actively transported thru bacterial cytoplasmic membrane
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3
Q

Tetracyclines Pharmacokinetics

A
  • Incomplete PO

*antacids/dairy products decrease PO absorption

  • Wide distribution; some CNS (25%), fetus and milk/nursing (50-60%)
  • Excreted primarily unchanged in the urine, accumulates in renal failure
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4
Q

Doxycycline Pharmacokinetics

A
  • PO almost complete
  • Most widely used tetracyline, long t1/2 (16-18hrs), usually once/day or BID administration
  • Excreted mostly by nonrenal mechanisms, via bile > feces as inactive conjugate or chelate, the only tetracycline that does not accumulate in renal insufficiency
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5
Q

Doxycline Use

A
  • Activity against Chlamydia trachomatis, anthrax, cholera, Lyme disease, Rocky Mountain Spotted fever (Rickettisiae)
  • Doxycycline + Cephalosporin against anaerobic bacteria
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6
Q

Minocycline Pharmacokinetics

A
  • Most lipid soluble tetracycline, 100% PO
  • Longest t1/2 (16-18hrs.)
  • Undergoes significant metabolism, mostly excretion of metabolites in urine and feces
  • Especially effective in treatment of acne due to increased penetration of skin
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7
Q

Tetracyclines Spectrum

A
  • Gm (+): susceptible species of staph/strep, however other drugs preferred due to bacteriostatic action/increased resistance (altered binding to 30S ribosomal site and inc. efflux of drug)

- B. burgdorferi (Lyme disease)

- Helicobacter pylori (GI ulcers)

- Main indications: Rickettsiae, mycoplasma pneumonia, Chlamydia trachomatis, V. cholera

  • Not effective against resistant Gonococci
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8
Q

Tetracycline Adverse Effects

A
  • Phototoxicity - reactions in skine exposed to sunlight, esp. demeclocycline>doxycycline
  • Skeletel effects - chelates teeth and bones during calcification
  • Contraindications: not to be used in children (<8yrs) or during pregnancy
  • Hepatotoxicity - esp. in pregnancy
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9
Q

Aminoglycosides MOA

A
  • Bacteriocidal, irreversible binding to 30S (and some 50S) to inhibit protein synthesis

*blocks initiation of synthesis

*blocks further translate and elicits premature termination

*incorporation of incorrect amino acid

  • Diffuses thru porin channels

*so used for gm (-)

  • Most common resistance due to production of microbial enzymes, acetylases, phosphorylases, adenylases; also impaired entry into bacterial cell and altered binding receptor protein on ribosome unit
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10
Q

Aminoglycosides

A
  • Gentamicin/Tobramycin
  • Netilmicin/Amikacin
  • Streptomycin
  • Toxicity both time and conc. dependent
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11
Q

Aminoglycosides Pharmacokinetics

A
  • Poor PO
  • Little if any CNS penetration, high conc. in renal cortex; why they are extremely nephrotoxic
  • Post-antibiotic effect that allows for large once/day dosing

*residual cidal effect that last longer tha MIC in plasma

  • Must adjust dosage in renal dysfunction proportional to creatinine clearance
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12
Q

Aminoglycosides Spectrum

A
  • Gm (+): limited, Staph> Strep; increased resistance, not used alone; used in combo w/Pens/Cephs for serious staph, strep, enterococcal infections>bacteriocidal synergism
  • Aerobic gm (-) is primary indication, the big guns, indicated for serious infections. Affects almost all gm(-). Adm w/3rd/4th gen. Pens for Pseudomonas
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13
Q

Streptomycin Use

A
  • Generally used in combo w/other drugs; deep IM injections
  • W/a Penicillin for enterococcal endocarditis
  • Tuberculosis, esp. w/multi-resistant strains, in initial therapy, IM adm
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14
Q

Gentamicin/Tobramycin Use

A
  • Gentamicin- most widely used systemic aminoglycoside; less expensive; active against Serratia species and better than Tobramycin when used in combination w/a Penicillin against enterococci; however, streptomycin is preferred w/Pen

- Tobramycin 2-4X more potent against Pseudomonas than Gentamicin; however, it is less effective against enterococci and ineffective against mycobacteria

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15
Q

Netilmicin/Amikacin Use

A
  • Netilmicin more resistant to microbial enzymes, used in Gentamicin resistance, otherwise it is comparable to these drugs
  • Amikacin exhibits the greatest resistance; used in Gentamicin and Tobramycin resistance; Amikacin less vulnerable to microbial enzymes b/c of protective side chain
  • Expensive
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16
Q

Aminoglycosides Toxicity

A
  • Ototoxicity- degeneration 8th nerve, contraindicated in pregnancy
  • Nephrotoxicity- inc BUN, preteinuria, inc serum creatinine, inabilti to conc. urine, adjust dose to creatinine clearance
17
Q

Aminoglycoside-like Drug

A
  • Spectinomycin
18
Q

Spectinomycin Use

A
  • Structurally related to aminoglycosides
  • Only used as alternative to treat gonorrhea in patients allergic to Pens/Cephs or where gonococci are resistant to other drugs (i.e., Fluoroquinolones)
  • May also be used during pregnancy
19
Q

Macrolides

A
  • Semi-synthetic derivative: azithromycin, clarithromycin

- Erythromycin

- Clindamycin

20
Q

Macrolides MOA

A
  • Alternate to Pen/Cephs when theres an allergy
  • Bacterial resistance when developed to one macrolide becomes common to other macrolides (i.e., alteration of binding site, methylation in gm (+) bacteria 50S ribosome site)
21
Q

Erythromycin MOA

A
  • Macrolide
  • Primarily bacteriostatic, binds 50S of bacterial ribosomes, inhibits protein synthesis
  • Resistance- change in ribosomal binding site (primary), inc. hydrolysis, dec. drug uptake/efflux pump
  • Decomposed by gastric HCL to irritant
22
Q

Erythromycin Spectrum

A
  • Gm (+): alternative to Pens/Cephs for strep and pneumococcal minor throat/ear infections
  • GM (-): Legionella pneumophila, Mycoplasma pneumonia, Genital infections: Chlamydia, syphilis, gonorrhea
23
Q

Clarithromycin Use

A
  • Macrolide
  • Increased gm (-) activity over other for Leg. pneumophila, C. trachomatis, Mycobacterium avium complex (AIDS); Helicobacter pylori, Borrelia burdorferi

- Inhibits hepatic drug metabolizing enzymes

24
Q

Azithromycin MOA

A
  • Macrolide

- Less GI irritation

  • Gm(+) strept activity = ERY; alternates to B-lactams for pharyngitis, sinusitis, community-acquired pneumonia
  • Increased gm(-) H. influenzae, N. gonorrhoeae, Chlamyida
  • Long t1/2 (2-3days)
25
Q

Clindamycin Spectrum

A
  • Gm(+) and anaerobes, Bacteroides/Clostridium, but not C.difficile
26
Q

Clindamycin Use

A
  • Main use: gm(+) strep and staph infections (e.g., bacterial endocarditis)
27
Q

Clindamycin Adverse Effects

A
  • GI/diarrhea, superinfections, esp. pseudomembranous colitis due to overgrowth of Clostridium difficile within GI tract
28
Q

Linezolid Use

A
  • Blocks early stage of protein synthesis, binds ribosomal RNA of 50S subunit
  • Indicated for MRSA, Vancomycin resistant Enterococcus faecium/E. faecalis (VREF), bacteriostatic
29
Q

Chloramphenicol MOA

A
  • Bacteriostatic, binds 50S, inhibits protein synthesis
30
Q

Chloramphenicol Spectrum

A
  • Broad spectrum: gm(+), gm(-), anaerobes
31
Q

Chloramphenicol Adverse Effects

A
  • Good PO, wide dist./CNS, metabolism glucuronidation (usu deficient in infants) “Gray baby syndrome”: depressed breath, CV collapse, cyanosis, abdominal distension, loose green stools, related to inhibition of mitochondria (70S)

- Inhibits CYP450 enzymes, drug interactions

- Bone marrow suppression

- Aplastic anemia; increased risk of leukemia in those who develop this and recover

CMBM Exam 4 (14 decks)

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