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Pharm > Tetracyclines ,Glyclines, Sulfonamides, Chloramphenicol and urinary tract agents > Flashcards

Tetracyclines ,Glyclines, Sulfonamides, Chloramphenicol and urinary tract agents Flashcards

1
Q

MOA: tetracylines (tetracycline, doxycycline and minocycline) and glycylcyclines (tigecycline)

A

They reversibly bind the 30S ribosomal subunit to inhibit the binding of aminoacyl transfer-RNA to the
acceptor (A) site on the mRNA-ribosomal complex. This prevents addition of amino acid residues on
elongating peptide chain.

Bacteriostatic; Bactericidal against very susceptible organisms

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2
Q

MOR: tetracylines

A
  • Acquisition of genes on mobile elements via efflux pumps, ribosomal protection proteins, and enzymes that deactivate drugs
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3
Q

Is there cross-resistance between tetracyclines?

A

Cross-resistance observed between tetracyclines, except

for minocycline

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4
Q

Which drug is not affected by the mechanisms of resistance?

A

• Tigecycline resistant to these mechanisms

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5
Q

Spectrum: tetracyclines

A

G+ aerobes (MSSA, PSSP is mostly susc.)
G- aerobes
Anaerobes

Rickettsia
Chlamydia
Mycoplasma
Spirochetes
Strep
Legionella
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6
Q

Spectrum: tigecycline

A

G+ aerobes (incl. MRSA)
G- aerobes (incl, VRE)
Anaerobes

Not proteus or pseudomonas

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7
Q

Treating bacteremias with tigecycline?

A

No

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8
Q

Treating UTIs with tigecycline?

A

No

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9
Q

Absorption of tetracyclines and glycylcyclines overall

A

 Absorbed best on an empty stomach

 Absorption impaired by di- and trivalent cations

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10
Q

Bioavailiability of tetracycline

A

60-80%

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11
Q

Bioavailiability of doxycyline and minocycline

A

90-100%

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12
Q

Affect of food on absorption of tetracyclines and glycylcyclines

A

Absorbed best on an empty stomach

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13
Q

What slows down tetracycline and glycylcycline absorption

A

Divalent and trivalent cations

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14
Q

Distribution: tetracyclines and glycylcyclines

A

Widely distributed with good penetration into synovial fluid,
prostate, seminal fluid

Minimal CSF penetration

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15
Q

Elimination: tetracyclines

A

Tetracycline - excreted unchanged in the

urine

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16
Q

Is dosage adjusted in renal failure?

A

Yes

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17
Q

Half lives of tetracycline and demeclocycline

A

Tetracycline half-life = 6 to 12 hours; demeclocycline half-life = 16 hours

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18
Q

Elimination of doxycycline, minocycline and tigecycline

A

Doxycycline and minocycline (metab) and tigecycline (biliary)

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19
Q

Do doxycycline, minocycline and tigecycline require dose adjustment in renal failure?

A

No

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20
Q

Do doxycycline, minocycline and tigecycline require dose adjustment in renal failure?

A

Doxy and mino do not

Tigecycline DOES

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21
Q

Are tetracyclines and tigecyclines removed during hemodialysis?

A

Minimally

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22
Q

Half-lives of doxy, mine and tige and dosing (general)

A

Half-lives are long, but they are all dosed every 12 hours!

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23
Q

Indications: tetra, doxy, mino, tige

A

Atypical pneumonia
STDs
Rickettsial infections, incl. rocky mountain fever

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24
Q

Specific indications: doxy

A
  1. Community-acquired pneumonia – due to PSSP, Mycoplasma spp, and Chlamydophila spp.
  2. Chlamydial infections including psittacosis, lymphogranuloma venereum,
    and nongonococcal urethritis
25
Q

Specific indications: tige

A

Polymicrobial infections caused by susceptible bacteria (not caused
by Proteus or Pseudomonas) in the following conditions:
1. Complicated skin and skin structure infections
2. Complicated intra-abdominal infections

26
Q

Can pregnant women take tetracyclines and tigecyclines?

A

No. They cause permanent tooth discolorations of primary dentition.

Children under 8 also shouldn’t take them.

27
Q

Adverse effects: tetracycline, minocycline, doxycycline

A 
GI
photosensitivity	
hepatotoxic
Discolor teeth (pregs + kids)
Fanconi syndrome	(if	
outdated)
28
Q

MOA: trimethoprim-sulfamethoxazole (sulfonamides)

Bactrim

A

Sulfamethoxazole: competitively inhibits dihydropteroate synthetase, preventing the incorporation of PABA into folic acid

Trimethoprim: competitively inhibits the activity of dihydrofolate reductase to prevent the reduction of dihydrofolate to tetrahydrofolate

Synergistically inhibit folate synthesis, stopping the production of DNA.

Bactericidal

29
Q

Resistance to Bactrim

A

Bacterial resistance is mediated by point mutations in dihydropteroate
synthase and/or altered production or sensitivity of bacterial dihydrofolate
reductase.

Resistance has been reported in E. coli, Klebsiella spp., Proteus mirabilis, H. flu, Salmonella spp, and Staph

30
Q

Spectrum: Bactrim

A

G+ aerobes: S. aureus (incl. some MRSA, esp. CA-MRSA), S. pyogenes, and Nocardia

G- aerobes: most Enterobacteriaceae and
Stenotrophomonas maltophilia.

DOC - Pneumocystis carinii/ jiroveci

TMP-SMX is NOT active against pseudomonas or anaerobes

31
Q

Indications: Bactrim

A

UTIs
Prostatitis
DOC- Pneumocystis carinii/jiroveci pneumonia
Skin and soft tissue infections due to CA-MRSA
Stenotrophomonas maltophilia infections

32
Q

Adverse Effects: Bactrim

A

GI, rash, bone marrow

supprxn, renal

33
Q

Drug Ixns: Bactrim

A

Warfarin

34
Q

MOA: chloramphenicol

A

Inhibits protein
synthesis by reversibly binding to the larger 50S subunit

Binding to the ribosome prevents attachment of the amino acid-containing end of the aminoacyl-tRNA to its binding region preventing peptide bond formation.

This mechanism produces a static effect against most bacteria except
H flu, Strep. pneumo and Neisseria meningitidis.

35
Q

Spectrum: chloramphenicol

A

G+ anaerobes: strep, NOT staph or enteroc

G- anaerobes: most, NOT pseudomonas

Anaerobes
Spirochetes
Rickettsiae
Chlamydiae
Mycoplasmas
36
Q

Absorption: chloramphenicol

A

Encapsulated form - great bioavailability

IV administration produces active chloramphenicol levels in serum that are 70% of those obtained after oral administration, because the drug is not completely hydrolyzed.

The iv preparation is the soluble but inactive drug that is rapidly hydrolyzed within the body
to become biologically active.

Intramuscular injection produces levels similar to iv administration but
may have delayed absorption from the injection site.

37
Q

Distribution: chloramphenicol

A

Due to high degree of lipid solubility, low protein bindingand small molecular size, chorampheicol diffuses well into tissues and body
fluids.

CSF levels are 30-50% of the serum concentration, even w/o meningitis

38
Q

Elimination: chloramphenicol

A

i. 90% liver, where it is
conjugated with glucuronic acid forming monoglucoronide.

Due to wide variation in the metabolism and excretion in children, dosage requirements
vary by age with lower daily doses in newborns.

ii. Monoglucoronide is excreted in the bile into the small intestine,
hydrolyzed by bacterial enzymes to aglycone, reabsorbed and conjugated with glucuronic acid again. This enterohepatic circulation results in about 80-90% of the monoglucoronide being excreted by the kidney.

39
Q

Toxicity: chloramphenicol

A

Narrow therapeutic window. Monitor newborns and premature infants, patients with
hepatic disease and patients taking interacting drugs. Peak serum levels should
be maintained between 15-25 g/mL and trough levels between 5-15 g/mL in
patients with meningitis, 10-20 g/mL in patients with other infections. Toxicity
occurs in those with levels 40 g/mL.

40
Q

In renal insufficiency, adjust dose?

A

No

41
Q

In hepatic insufficiency, adjust dose?

A

Yes - decrease dose

42
Q

Indications: chloramphenicol

A

Not a first line treatment in the US

Developing countries:
Infant Meningitis w/
pcn allergy Rickettsia in kids and preg

43
Q

Adverse effects: chloramphenicol

A

BM supprxn

Gray Baby

44
Q

Drug ixns: chloramphenicol

A

A. Phenobarbital reduces serum concentrations of chloramphenicol by 30-40% with
increased concentrations of Phenobarbital by 50%.
B. Cyclosporine concentrations increased by chlorampnenicol increasing the risk for
renal dysfunction, cholestasis, paresthesias.
C. Decreased effectiveness of cyclophosphamide due to decreased metabolism to
active cyclophosphamide.
D. Rifampin/rifabutin decreases chloramphenicol levels
E. Reduces tacrolimus blood concentrations.

45
Q

MOA: Nitrofurantoin

A

May require
enzymatic reduction within the bacterial cell wall. The reduced compounds are
capable of binding to ribosomal proteins.
Nitrofurantoin has also been shown to
inhibit synthesis of inducible enzymes by blocking translation and also to inhibit
bacterial respiration and pyruvate metabolism.

46
Q

Spectrum: Nitrofurantoin

A

E. coli, Citrobacter sp, GBS, Staph

saprophyticus, Enterococcus (incl. many VRE strains)

47
Q

Bioavailability: nitrofurantoin

A

40-50%.

Absorption occurs rapidly in the small intestine and is enhanced with food.

48
Q

Distribution: nitrofurantoin

A

Urine concentrations are substantial
Low to undetectable serum concentrations after standard oral doses.
Does not go to prostate

Short half-life

49
Q

Elimination: nitrofurantoin

A

Mostly kidneys, involving

filtration, secretion, and reabsorption.

50
Q

Increase or decrease nitrofurantoin in kidney failure

A

Increase in renal failure, because we want more drug at the urethra

51
Q

Counterindications: nitrofurantoin

A

Renal insufficiency

Elderly

52
Q

MOA methenamine

A

Becomes formaldehyde at an acidic pH and denature proteins and DNA
Don’t use with proteus

53
Q

MOR methenamine

A

Alkaline urine makes it harder for drug to kill things

54
Q

Counterindications : methenamine

A

avoid with gout and liver insufficiency

55
Q

Spectrum: methenamine

A

Not really…it makes it harder for things to live

56
Q

Absorption: methenamine

A

82-88% recovery in urine

Enteric-coated formulations reduce degradation but also take longer to absorb

57
Q

Distribution: methenamine

A

Broad distribution in tissue, incl. breastmilk

58
Q

Indication: methenamine

A

Prophylaxis in people with frequent UTIs

Not effective in preventing UTIs in patients with chronic, indwelling urinary catheters

59
Q

Adverse effects: methenamine

A

Gi, rash, prutitus, cystitis, neuropathy, anemia

Pharm (22 decks)

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