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Infectious Diseases > Antibiotics > Flashcards

Antibiotics Flashcards

1
Q

Amoxicillin: renal and hepatic dose adjustments

A

Primarily eliminated by kidneys
Renally reduce dose if eGFR < 30

No hepatic dose adjustment

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2
Q

Antibiotics most associated with pseudomembranous colitis

A

Amoxicillin/penicillins, clindamycin, cephalosporins and fluoroquinolones

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3
Q

Cell wall active antibiotics (bacteriocidal)

A

BETA LACTAMS

  • Penicillins
  • Cephalosporins
  • Monolactams
  • Carbapenems

GLYCOPEPTIDES

  • Only slowly bactericidal, act more bacteriostatic
  • LESS effective than beta lactams against sensitive organisms
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4
Q

Antibiotics that cause inhibition of protein synthesis (bacteriostatic)

A
  • Aminoglycosides (EXCEPTION to the rule - actually bacteriocidal)
  • Macrolides
  • Tetracyclines
  • Lincosamides
  • Oxazolidinones
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5
Q

Antibiotics with other MOA (not cell wall, not inhibition of protein synthesis)

A
  • Nitroimidazoles (DNA strand breakage)
  • Quinolones (DNA gyrase inhibitors)
  • Trimethoprim and sulphas (anti folate agents - relative selectivity for bacterial enzymes)
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6
Q

Penicillins

  • MOA
  • Bacteriostatic or cidal
  • Excretion
  • Key A/E
A
  • Cell wall active
  • Bactericidal
  • Renally excreted
  • Generally safe - allergy is main A/E
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7
Q

Penicillin (drug):

  • Routes
  • Spectrum
  • Excretion
  • A/E
A
  • Oral, IM, IV

Spectrum:

  • Drug of choice: strep and listeria
  • Enterococci and anaerobes (not bacteroides)
  • Most staph and gram negs now resistant

Renally excreted

Safe unless allergic

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8
Q

“enteric active” penicillins:

  • Drugs
  • Spectrum
  • Excretion
  • A/E
A

Drugs:
- Amoxicillin (PO, IV), ampicillin (IV)

Spectrum:

  • Enterococci (DOC)
  • Strep (avoid with EBV - rash)
  • Anaerobes (not bacteroides)
  • Most gram negatives now resistant
  • not great for staph

Renally excreted
Safe unless allergic

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9
Q

“Antistaph” penicillins

  • Drugs
  • Spectrum
  • Toxicity
A

Drugs:
- Flucloxacillin (PO/IV) & dicloxacillin (PO)

Spectrum:
Exclusively gram positive
- Staph (MSSA) DOC
- Strep (less effective than penicillins)
- NOT enterococci, gram negatives, anaerobes

A/E:

  • Allergy
  • Hepatotoxicity! Esp in elderly
  • Irritates veins
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10
Q

“Antipseudomonal” penicillins:

  • Drugs
  • Spectrum
  • Toxicity
  • When to use
A

Drugs:
- Ticarcillin/piperacillin
(not as individual drugs anymore)

Spectrum:

  • Gram negatives including pseudomonas
  • Strep
  • Staph (not MRSA)
  • Enterococci
  • Anaerobes (not bacteroides)

Toxicity:
- Allergy

BROAD SPECTRUM - ONLY USE WHEN SERIOUS GRAM NEG SEPSIS IS SUSPECTED

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11
Q

Pencillins with B-lactamase inhibitors

  • Drugs
  • Spectrum
  • Toxicity
A

Drugs:

  • Augmentin (PO): amoxi + clavulanic acid
  • Tazocin (IV): piperacillin + tazobactam
  • Timentin (IV): ticarcillin + clavulanic acid

Spectrum:

  • Staph (not MRSA)
  • Strep
  • Enterococci
  • Gram negatives
  • Pseudomonas (only timentin/tazocin)
  • Anaerobes

Toxicity:

  • Allergy (augmentin) - rash in EBV
  • Clavulanic acid/tazobactam can cause hepatotoxicity
  • Augmentin: GI upset

BROAD SPECTRUM AGENTS - not first line, but useful when wide range of potential pathogens exists

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12
Q

ALL enterococci are intrinsically resistant to ALL….

A

Cephalosporins!

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13
Q

Cephalosporin generations and their spectrums

A 
1st generation (cephalexin, cephazolin):
- Staph (not MRSA), strep and limited gram negatives
2nd generation (cefuroxime):
- As above + haemophilus

3rd generation (ceftriaxone):

  • Gram negatives and strep
  • Does NOT cover pseudomonas
  • Limited staph cover

4th generation (cefepime, ceftazidime):

  • Gram negatives (including pseudomonas)
  • Some staph cover, strep (cefepime)

5th generation (ceftaroline):

  • Gram negs + MRSA activity
  • limited pseudo

Cephalosporins - increasing gen, less staph cover, more gram neg cover
4th gen covers pseudomonas

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14
Q

Cephalosporins:

  • Indications
  • A/E
A

Indications:

  • Consider in penicillin allergic patients
  • Gram negative cover in renal impairment or pregnancy
  • Meningitis

A/E:

  • Hypersensitivity
  • Broad spectrum - overuse strongly associated with development of VRE
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15
Q

Monobactams

  • Drugs
  • Spectrum
  • Toxicity
  • Indications
A

Drugs: aztreonam (IV)

Spectrum: gram negatives including pseudomonas
(NO gram pos, anaerobes)

A/E: hypersensitivity

Indications: limited. Serious gram negative infections resistant to other agents

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16
Q

Carbapenems:

  • Drugs
  • Spectrum
  • Toxicity
  • Excretion
A

Drugs: meropenem (IV)

Spectrum: INSANELY broad – most bacteria except MRSA and ampicillin resistant enterococci

Toxicity: allergy - but often safe in pencillin allergic pt, seizures

Renally excreted

17
Q

Glycopeptides

  • Drugs
  • Spetrum
  • Problems
A

Drugs: vancomycin (IV) or teicoplanin (IV or IM)

Spectrum:

  • Gram positive aerobes only
  • First line for MRSA and ampicillin R enterococci

Problems:

  • VRE
  • 100% renally excreted - needs levels monitored
  • Synergistic nephrotoxicity with aminoglycosides
  • Red man syndrome
18
Q

Beta lactam antibiotic table - see studying w pictures ppt slide 2

A

…

19
Q

Aminoglycosides

  • Drugs
  • Spectrum
  • Excretion
  • Toxicity
A

Drugs: gentamicin (IV or IM), tobramycin, amikacin

Spectrum:

  • Gram negs including pseudomonas
  • Used for synergy in staph and enterococcal endocarditis

Renally excreted (dose adjust)

Toxicity:

  • MUST monitor levels
  • Nephrotoxic, ototoxic (hair cells)
  • Vestibular dysfunction

Most indications do not need more than 48 hours aminoglycoside therapy

Can be effective and cheap if used well

20
Q

Macrolides

  • Drugs
  • Spectrum
  • Toxicities
  • Uses
A

Drugs: Erythromycin (oral or IV), roxithromycin, clarithromycin, azithromycin

Spectrum:

  • Varies
  • Staph and streph
  • Atypical organisms including legionella

Toxicities:

  • Sclerosing to IVC
  • GIT upset with all forms
  • Hepatotoxicity
  • Drug interactinos

Uses:

  • PO rx less serious pneumonia
  • Minor gram +ve infections in beta lactam allergic pt
  • Atypical organisms: chlamydia, legionella
21
Q

Tetracyclines

  • Drugs
  • Spectrum
  • Toxicity
A

Doxycycline (PO)

Spectrum:

  • Complex
  • Mainly used against atypicals: malaria prophylaxis, chlamydia spcc, rickettsia

Toxicity:

  • Photosensitivity
  • Erosive oesophagitis
  • Deposits in teeth/bones of children/fetus - CI in children and pregnancy
22
Q

Lincosamides

  • Drugs
  • Spectrum
  • Bioavailability
  • TZoxicity
A
  • Clindamycin (PO, IV), licomycin (IV)
  • Spectrum: staph (some strains of MRSA), strep, anaerobes
  • Excellent PO bioavailability
  • Toxicity: GIT upset (PO), c diff
23
Q

Oxazolidinones

  • Drugs
  • MOA
  • Bioavailability
  • Spectrum
  • Toxicities
  • Uses
A
  • Linezolid (PO or IV)
  • Inhibits initiation of protein synthesis
  • 100% PO bioavailability

Spectrum: gram positives inc MRSA

Toxicities:

  • Dose related myelosuppression (esp thrombocytopenia)
  • Peripheral neuropathy
  • Minor AEs - bad taste, rash, GIT upset

Uses:
- Never first line
- Treatment of resistant gram positive organisms
or unable to tolerate better options

24
Q

Nitroimidazoles

  • Drugs
  • Spectrum
  • Bioavailability
  • Toxicity
A
  • Metronidazole (PO or IV)
  • Spectrum: anaerobes (first line drug)
  • Excellent PO bioavailability
Toxicity
Metallic taste
GIT upset
Interaction with alcohol 
Peripheral neuropathy

DOC for c diff colitis

25
Q

Quinolones

A

Drugs: ciprofloxacin (PO or IV)

Spectrum:

  • Gram negatives including pseudomonas
  • Sometimes used in combinations against staph
  • Atypical organisms

Excellent bioavailability

Toxicity:

  • tenosynovitis
  • possible cartilage problems in children/foetus

Newer quinolones e.g. moxiflox have better gram positive activity

26
Q

Trimethoprim

  • Spectrum
  • Main use
  • TOxicity
A

Spectrum: limited gram negative and positive aerobes

Main use - UTIs

Toxicity: rash/itch, may increase serum K+ (blocks distal tubular secretion of K+ and reabsorption of Na+) and may increase serum Cr (competes for tubular secretion of Cr)

27
Q

Trimethoprim / sulphamethoxazole (PO, IV)

A

Spectrum: gram negative aerobes, gram positive aerobes, some atypicals (DOC for PJP)

Toxicity:
GI upset
Rash common (poss. Steven Johnson)
Bone marrow suppression 
All trimethoprim A/E can also occur

Mainly used for chest sepsis, urinary sepsis, PJP prophylaxis or treatment

28
Q

Mechanism of resistance in VRE?

A

VAN A and VAN B genes !!

Alteration of the peptidoglycan synthesis pathway -

D-Ala-D-Ala becomes D-Ala-D-Lac or D-Ala-D-Ser

29
Q

UTI caused by VRE ?

A

Despite being a VRE, antibiotic of choice is still amoxicillin due to large amounts of amoxi concentration you can achieve in the urine

Infectious Diseases (13 decks)

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