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Micro Exam 1 > Pogue: Antimicrobials IIb > Flashcards

Pogue: Antimicrobials IIb Flashcards

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1
Q

Macrolides

MOA:

Bacteriostatic or Bactericidal?

A

Bind to the 50S subunit of the ribosome

Bacteriostatic

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2
Q

Macrolides

Agents (of clinical relevance)

A

Erythromycin (IV/PO)
Clarithromycin (PO)
Azithromycin (IV/PO)

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3
Q

Macrolides

Spectrum of activity

A

The respiratory pathogens

C.trachomatis: causes Chlamydia

Mycobacterium avium complex (MAC)

H.pylori: clarithromycin

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4
Q

The respiratory pathogens:

A 
Streptococcus
H.influenzae
M.catarrhalis
Mycoplasma pneumonia
Chlamydia pneumonia
Legionella pneumophilia
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5
Q

What treats against MAC?

A

Mycobacterium avium complex (MAC): clarithromycin and azithromycin

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6
Q

What treats H.pylori?

A

Clarithromycin

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7
Q

Macrolides

Side effects
Biggest class concern:
Worst with what? Why?
Much less with what?

A

Biggest class concern: nausea/vomiting/diarrhea

–Worst with erythromycin as it binds to the motolin receptor in the GI tract
•Pearl: erythromycin actually used as promotility agent in hospital for severe constipation

–Much less with azithromycin

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8
Q

Macrolides

Other side effects:

A 
QT prolongation (pro-arrhythmia)
Rare hepatotoxicity
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9
Q

Macrolides

Clinical Uses:

A

Respiratory Tract Infections: azithromycin first line for CAP (also used in traceobronchitis, COPD exacerbations)

H.pylori: clarithomycin part of standard therapy

Mycobacterial regimens: clarithromycin and azithromycin

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10
Q

Macrolide Resistance:

A

Target-Site Modification: change in the 50S subunit binding site

Decreased Concentration in the Cell: efflux pumps

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11
Q

Macrolide

IV dose =
Azithromycin half life:
Metabolism
DDIs
Renal dosing
A

IV dose = PO dose
Azithromycin long half-life
–~ 72 hours; allows shorter course of the drug

Metabolism
–Inhibitors and substrates of CYP3A4

Many drug interactions

No renal dose adjustment needed

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12
Q

Macrolide

DDIs:

A

Erythromycin and clarithromycin are the big players here

Azithromycin much less

Why azithromycin is the workhorse for this class

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13
Q

What is first line medication for CAP?

A

Azithromycin

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14
Q

What are ketolides?

What is Telithromycin?

A

Ketolides are antibiotics belonging to the macrolide group

Telithromycin is the first ketolide antibiotic to enter clinical use and is sold under the brand name of Ketek.

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15
Q

Ketolides: Telithromycin

General:

Spectrum of Activity:

Clinical Use:

A

Derivative of macrolides

Spectrum of Activity:
- Similar to azithromycin, with enhanced activity against S.pneumo

Clinical Use:

  • Originally thought to be a niche drug for CAP
  • High rates of hepatotoxicity has limited use clinically
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16
Q

TETRACYCLINES:

MOA:

Bacteriostatic or Bactericidal?

A

MOA: ribosomal antibiotic that works on the 30S subunit of the ribosome

Bacteriostatic

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17
Q

TETRACYCLINES:

Pharmacokinetics:

A

Highly lipophilic: penetrates tissues well

Not highly renally eliminated: but still sufficient for UTI

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18
Q

Tetracycline Agents (3):

What is used for SIADH?

A

Tetracycline (PO)

Doxycycline and Minocycline (IV/PO): most often used

Demeclocycline (PO): used for SIADH

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19
Q

Doxycylin and Minocycline

Spectrum of activity:
G+
G-
Anaerobic activity
Miscellaneous: has activity against (2)
A

Gram (+) Activity:
S.pneumo
S.aureus (including MRSA)
enterococcus

Gram (-) Activity:
H.influenzae
M.catarrhalis
may also have activity against enterobacteraciae (including MDRO)

Anaerobe Activity: variable

Miscellaneous: has activity against
o Atypical pneumonia pathogens
o Organisms associated with animal bites (Lyme disease)

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20
Q

Clinical Use (Doxycyclin and Minocyclin) (3):

A

Respiratory tract infections (including CAP)

UTIs

Skin and soft tissue infections (particularly when community acquired-MRSA is a concern)

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21
Q 
Tetracycline 
Adverse Effects (3):
A

N/V/D: lessened with food

Binding to growing teeth and bones: avoid if less than 8 years old

Photosensitization

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22
Q

Tetracycline

Drug Interactions:

A

Chelate with divalent and trivalent cations

Do not take with multivitamins!

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23
Q

What are Glycylcyclines?

What is Tigecycline?

A

Glycylcyclines are a new class of antibiotics derived from tetracycline.

Tigecycline is a glycylcycline antibiotic

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24
Q

Tigecycline:

MOA:

Pharmacokinetics:

Study These Flashcards
A

First in this new class that is a derivative of the tetracyclines

MOA: same as tetracycline (bind 30S subunit of ribosome); also bacteriostatic (?)
o However, has a different structure and has the ability to overcome some of the tetracycline-resistance mechanisms (efflux pumps, target-site alterations)

Pharmacokinetics:
- Same as tetracycline

25
Tigecycline ``` Spectrum of Activity: G+ G- Anaerobic Notable holes ```
Gram (+) Activity: broad (includes MRSA and VRE) Gram (-) Activity: similar to tetracyclines, but also includes resistant organisms (ESBL, Acinetobacter) Anaerobic Activity: some coverage Notable Holes: pseudomonas and proteus (and providencia)
26
Tigecycline Clinical use (3): Adverse reactions:
Clinical Use: Last line option for many nasty Gram (-) bugs: o Carbapenem-resistant acinetobacter o Klebsiella Polymicrobial wounds: including MRSA or VRE 2nd line therapy for pts with penicillin allergies for multiple disease states Adverse Reactions: - Nausea and vomiting: 20% of patients - Pancreatitis: few cases noted in post marketing analysis
27
LINCOSAMIDES MOA: Bacteriostatic or Bactericidal? Agents (2):
Acts on 50S subunit of the ribosome to prevent protein synthesis Bacteriostatic Lincosamide Agents: 1. Lincomycin: been completely replaced by clindamycin (increased activity) 2. Clindamycin
28
Spectrum of Activity (Clindamycin): G+ G- Anaerobes
Gram (+) Activity: S.aureus (including MRSA), Streptococcus (usually) o Note: has toxin suppression activity and necrotizing Gram (+) infections Gram (-) Activity: NONE Anaerobes: good (better for oral anaerobes than lower GI anaerobes)
29
Clinical Uses (Clindamycin) (3):
Skin infections: because of staphylococcus (including MRSA) and streptococcus coverage Aspiration pneumonia: since anaerobes are thought to play a role (but NO Gram (-) coverage) Alternative for anaerobic coverage
30
Side Effects (Clindamycin):
Diarrhea: in both PO and IV formulations Nausea C.difficile Diarrhea: used to be the number one antibiotic associated with C.diff (now FQ and other broad spectrum agents)
31
Macrolide-Lincosamide-Streptogramin (MLS) resistance seen in what? S.aureus can posses: Can lead to: How do you detect presence of erm gene?
Macrolide-Lincosamide-Streptogramin (MLS) Resistance in S.aureus: S.aureus can posses an erm gene that can encode resistance to all 3 classes (all bind 50S subunit) Can lead to inducible clindamycin resistance when isolate says “erythromycin resistant and clindamycin susceptible” Can use a special D test to detect presence of the erm gene
32
Sulfonamides: MOA What does PABA do? Bacteriostatic or Bactericidal? Most commonly used agent:
MOA: structural analog of PABA, which blocks the production of dihydrofolic acid Folic acid --> DHF --> THF --> Thymidines, purines Bacteriostatic Most commonly used agent: sulfamethoxazole (combined with trimethoprin= BACTRIM) Bactrim (TMP/SMX): together, the two become bactericidal (synergy)
33
What is Trimethoprin?
Inhibitor of dihydrofolic acid reductase (next step in the production of purines and DNA); also bacteriostatic
34
Spectrum of Activity (TMP/SMX): G+ Anaerobic Miscellaneous:
Gram (+): staphylococcus (including MRSA), some streptococcus (notably lacks group B strep), no enterococcus Anaerobic: minimal Miscellaneous: o Listeria and Nocardia o DOC for Stenotrophomonas maltophilia
35
What is the DOC for Stenotrophomonas maltophilia?
TMP/SMX
36
Spectrum of Activity (TMP/SMX): G- Pseudomonas
Gram (-): Enteric Gram negatives (variable; Klebsiella, Proteus, E.coli) SPICE organisms (limited clinical use for these) No pseudomonas coverage
37
Clinical Applications (TMP/SMX):
Outpatient UTIs: most commonly used agent for these Skin infections when MRSA is a concern: but remember, no coverage of group B strep DOC for many nasty infections: o PCP (pneumocystis) pneumonia o Stenotrophomonas maltophilia o Nocardia Treatment of multi-drug resistant Gram-negatives: role still debated
38
What is the most commonly used agent for outpatient UTIs?
TMP/SMX
39
What is the DOC of Nocardia and PCP Pneumonia?
TMP/SMX
40
TMP/SMX | Side Effects:
Hypersensitivity Reactions: most common agents that cause these (~3% of patients) - Simple rash --> Severe skin reactions (SJS/TEN) High concentrations can crystallize in the urine (Rare) TMP SEs: o Bone marrow suppression: anemia, leucopenia, and granulocytopenia o Hyperkalemia
41
TMP/SMX | DDIs:
Increased INR (How thin blood is) when given with warfarin: INR is the measurement that indicates if warfarin is at therapeutic levels or not
42
NITROIMIDAZOLES: MOA Pharmacokinetics: Agents:
MOA: not clearly defined; interaction with DNA that causes a loss of the helical structure and strand breaking, leading to cell death Pharmacokinetics: - ~100% bioavailability - Minimal renal elimination Agents: - Metronidazole - Tinidazole
43
Spectrum of Activity (Metronidazole):
ANAEROBES ONLY: better for lower GI anaerobes vs. mouth anaerobes (opposite of clindamycin) o DOC for C.difficile** - Some parasitic activity: T.vaginalis
44
What is the DOC of C.difficile?
Metronidazole - Mild | Vanco - Severe
45
Clinical Applications (Metronidazole): Side Effects: Drug Interactions:
Clinical Applications (Metronidazole): - Anaerobic coverage for nosocomial patients - DOC for C.diff - T.vaginalis Side Effects: - N/V - Metallic taste - Disulfuram reaction with ethanol - Peripheral neuropathies (rare) Drug Interactions: - Increased INR when given with warfarin
46
Drugs with anaerobic coverage (8)
``` Metronidazole Penicillin B-lactam/B-lactamase inhibitors –Piperacillin/tazobactam, ampicillin/sulbactam Clindamycin Cephamycins Carbapenems Moxifloxacin Tetracyclines (some) ```
47
RIFAMPIN MOA: Pharmacokinetics: Spectrum of Activity: G+: G-: Miscellaneous:
MOA: binds to b-subunit of DNA-dependent RNA polymerase, blocking RNA synthesis Pharmacokinetics: - ~100% bioavailability (IV dose=PO dose, but food may delay absorption) - No renal dosing necessary Spectrum of Activity: Gram (+): S.aureus (including MRSA) and streptococcus; not used as monotherapy Gram (-): used in combination with cell wall agent for synergy; minimal activity alone Miscellaneous: standard therapy for mycobaterial infections
48
RIFAMPIN Clinical Application: Side Effects:
``` Clinical Application: - Synergy: o Severe staph infections o Multi-drug resistant gram (-) bacilli - Mycobacterial infections: part of standard TB regimen ``` Side Effects: - Hepatotoxicty (HIGHLY)** - Discolored fluids
49
RIFAMPIN Drug Interactions:
STRONG inducer of multiple CYP450 isoenzymes** Contraindicated with many HIV meds Significant interactions with: o Antifungals o Anti-hypertensives o Statins
50
What is part of the standard therapy for mycobaterial infections?
Rifampin
51
POLYMIXINS: MOA: Bacteriostatic or Bactericidal? Why was use abandoned? What lead to re-emergence?
MOA: Cationic detergent that damages the cytoplasmic membrane, leading to leakage of intracellular substances and rapid cell death Electrostatically interacts with the LPS outer membrane of G- organisms Bactericidal Originally utilized in the 1950s Associated with high rates of nephrotoxicity and neurotoxicity, so use abandoned; Multi-drug resistance Gram negatives in the 1990s lead to re-emergence
52
POLYMIXINS Agents: Pharmacokinetics:
Agents: - Colistin (IV) - Polymixin B (IV,PO,topical) Pharmacokinetics: - Poorly understood
53
POLYMIXINS Spectrum of Activity: G+ G- Anaerobic
Gram (+): NONE Gram (-): Pseudomonas, A.baumannii, K.pneumoniae, E.coli; No activity against serratia and proteus Anaerobic: NONE
54
Clinical use Adverse events DDIs
Clinical Use: - Mulit-drug resistant gram (-) organisms in the hospital: when there are no other options! o Usually pseudomonas, A.baumannii, and K.pneumoniae (KPC- carbapenamase producing organism) Adverse Events: - Nephrotoxicity: up to 40% of patients; dose dependent and reversible - Neurotoxicity: parasthesias Drug Interactions: - Additive toxicities
55
Antipseudomonal Agents (Full List)
``` Piperacillin, Piperacillin/Tazobactam Cefepime, Ceftazadime Meropenem, Imipenem, Doripenem Aztreonam Gentamicin, Tobramycin, Amikacin Ciprofloxacin, Levofloxacin Polymixins ```
56
CHLORAMPHENICOL: MOA: Clinical Use: Side Effects:
MOA: ribosomal 50S inhibitor Clinical Use: not clinically used any more due to toxicity Side Effects: - Bone Marrow Suppression: dose-dependent - Aplastic Anemia: non-dose dependent - Gray-Baby Syndrome
57
Gray-Baby Syndrome:
SE of Chloramphenicol Lack of an enzyme in phase II metabolism of the drug; leads to accumulation of a toxic metabolite (causes graying of the skin and cyanosis, among other symptoms)
58
NITROFURANTOIN: ``` MOA: Spectrum of Activity: Clinical Use: Side Effects: Contraindications: ```
MOA: inhibition of a variety of bacterial enzyme systems interfering with metabolism Spectrum of Activity: organisms causing UTIs Clinical Use: only to treat lower UTIs (First line) Side Effects: rare inflammatory lung process Contraindications: cannot use if GFR <60mL/min (completely filtered by the kidney)
59
DAPSONE: MOA: Clinical Use: Side Effects:
MOA: antagonist of PABA (similar to sulfa drugs) Clinical Use: prevention/treatment of PCP pneumonia when TMP/SMX cannot be used (ie. allergy) Side Effects: hemolysis; generally infrequent but more common in patients with G6P deficiency

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