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Pharmacology > Antibiotics > Flashcards

Antibiotics Flashcards

1
Q

What are the beta-lactam antibiotics?

A

Penicillins

Cephalosporins

Carbepenems

Monobactam

Beta-lactams inhibit transpeptidation of NAG and NAMs in bacterial cell walls

β-lactam antibiotics kill bacterial cells only when they are actively growing and synthesizing cell wall.

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2
Q

Beta-lactam - routes and general uses

A

Given Oral, IV, IM

Intrathecally is contraindicated

Poor CSF penetration, can reach therapeutic levels when meninges are inflamed.

T>MIC

Renally excreted - OAT

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3
Q

which beta-lactam antibiotics can treat CNS infections regardless of meningeal inflammation?

A

3rd generation cephalosporins - ceftriaxone and cefotaxime

2nd gen cephalosporin - cefuroxime

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4
Q

Mechanisms of resistance to β-lactam antibiotics

A

1 - penetration (intracellular organisms)

2 - Porins (like in gram-neg, need to get through porins in outermembrane to get to the peptidoglycan)

3 - pumps - drug efflux

4 - PBPs with low affinity for drug (penicillian binding protein)

5 - Penicillinases - hydrolyze (inactivate) drug

6 - peptidoglycan - organisms without cell wall (mycoplasma)

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5
Q

beta lactam resistant bacteria come in different classes,

A

Class A - Extended Spectrum Beta-lactamases - through several genes: TEM, SHV, CTX-M and KPC (klebsiella) Carbapenemase

Class A is passed by conjugation, expressed by gram-neg species especially

Class C – with genes AmpC and CMY organism displays resistance to broad and extended-spectrum beta-lactams

Class D – OXA-type: ESBLs and Carbapenemases

Class B -- genes: IMP, VIM, GIM, SPM, SIM: Carbapenemases. New Delhi (NDM-1): Carbapenemases
(class B type metallo-beta-lactamases)
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6
Q

How do bacterial biofilms affect therapy?

A

bacteria in biofilms are much less sensitive to antibiotics and tend to have decreased rates of growth

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7
Q

Hypersensitivity reactions to penicillins

A

Anaphylaxis: Rapidly progressive, life-threatening
-hypotension, bronchonstriction

angioedema, serum sickness (delayed, type III), immune hemolysis, rash or SJS

Fever; interstitial nephritis; vasculitis; neutropenia and
thrombocytopenia

Rx – Airway management, epinephrine followed by respiratory and cardiovascular support. Antihistamines or GCs as needed.

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8
Q

Name the non-immunologic side effects of beta-lactams

A

GI: mild to severe diarrhea; nausea; vomiting

Clostridium difficile infection - significant, pseudomembranous colitis

candidiasis infection

IM - pain, sterile imflammatory rxn at inj site, IV - phlebitis or thrombophlebitis

Intrathecal use is CONTRAINDICATED It can cause arachnoiditis or severe, fatal encephalitis

c. diff - gram pos, spore-forming, anaerobic bacillus

phlebitis - inflammation of vein wall

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9
Q

Drug Interactions of beta lactams

A

inhibition of OAT messes with probenecid and methotraxate

decreases effectiveness of oral contraceptives by decreasing estrogen recycling

interacts with gastric acid suppressors which increases c diff risk

tetracycline - reduce beta-lactam efficacy

decreases thyphoid vaccine efficacy

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10
Q

Natural Penicillin - What organisms do they treat?

A

useful for gram positive aerobes and anaerobes, N. meningitidis; H. influenzae; spirochetes

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11
Q

How are the different forms of natural penicillins administrured?

A

Penicillin G - IV and IM

Penicillin V - oral

repository Penicillin G - IM

  • Penicillin G procaine
  • Penicillin G benzathine
  • Penicillin G benzathine / procaine combo

poor penetration of CSF, inflamed meninges increases penetration

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12
Q

Resistance and cautions to Natural Penicillins

A

Beta-lactamases — s. aureus and gram-neg bacilli

PBPs with low affinity for beta-lactams —- s. pneumoniae, s. aureus, enterococcus faecium

gram-neg bacilli - drug cant pass through porins and have beta-lactamases

cautions - hypersensitivity, seizures, electrolyte distrurbances

jarisch-herxheimer reaction - complication of treatment of syphilis, thought to be a response to lipoproteins released by dying treponema pallidum

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13
Q

Penicillinase-Resistant Penicillins - name the drugs

A

Nafcillin
Oxacillin
Dicloxacillin
Cloxacillin

methicillin was the first in the class

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14
Q

Activity and therapeutic uses of penicillinase-resistant penicillins

A

activity against penicillinase-producing, methicillin-sensitive Staph aureus and Staph epidermidis

used for MSSA and MSSE

should not be used when penicillin can do the job

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15
Q

Resistance to penicillinase-resistant peniceillin and Adverse Effects

A

resistance - alteration of PBPs, expression of PBP2a (MecA gene) and inherent resistance (enterococci and listeria)

adverse effects special to these drugs are hepatitis and interstitial nephritis

hepatitis is through direct toxicity and hypersensitive rxn

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16
Q

Aminopenicillins - what are they?

A

extended spectrum penicillins

ampicillin (sometimes given with sulbactam)

amoxicillin (sometimes given with clavulanate)

Activity of Penicillin G plus Extended spectrum: gram-negative

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17
Q

Resistance to aminopenicillins

A

Class A TEM-1/SHV-1 β-lactamases found in H. influenza, N gonorrhoeae, E coli and klebsiella

Altered PBPs found in MRSA, pneumoniae, enterococcus

bacteroided fragilis - can be overridden with beta-lactamase inhibitor

Pseudomonas aeruginosa: inherently resistant

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18
Q

Adverse Effects of Aminopenicillins

A

non-allergic rash – pruritic maculopapular rash

viral infection - mononucleosis (EBV)

hypersensitivity reaction

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19
Q

Ampicillin-sulbactam: Broad use

A

parenteral only

includes repiratory, intra-abdominal, UTI and endocarditis

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20
Q

Amoxicillin-clavulanate Use

A

oral only

Respiratory, skin/skin structure, bite wounds and UTIs

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21
Q

Antipseudomonal Penicillins

A

Extended-spectrum penicillins

Piperacillin- tazobactam

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22
Q

Piperacillin-tazobactam

A

able to pass through porins in outer membrane because of polar side chains – pseudomonas aeruginosa and Enterobacteriaceae

broadest antibacterial spectrum of penicillins

Used for resistant gram-negative bacteria
-P. aeruginosa, indole-positive Proteus, Enterobacter

monotherapy is not recommended for p. aeruginosa - give with tobramycin or ciprofloxacin

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23
Q

Adverse Effects of Piperacillin-tazobactam

A

special effects of drugs:

exacerbation of CHF - drugs are manufactured as Na+ salts

abnormal platelet aggregation, thrombocytopenia

leukopenia and neutropenia with long-term use

seizure disorders

rash - especially in piperacillin use

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24
Q

β-Lactamase Inhibitors

A 
Clavulanic acid
Sulbactam
Tazobactam
Avibactam
Vaborbactam
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25
Q

Mechanism of β-Lactamase Inhibitors

A

suicide inhibitors - molecules bind irreversibly to and inhibit bacterial beta-lactamases

They are not antibiotics

Most active against Ambler class A beta lactamases

staphylococci N gonorrhoeae E coli
H influenzae K pneumoniae
M catarrhalis salmonella
B fragilis shigella

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26
Q

Cephalosporins

A

First-generation - Cefazolin, Cephalexin

Second-generation - Cefuroxime, Cefoxitin

Third-generation - Ceftriaxone, Cefotaxime, Cefdinir, Ceftazidime, Ceftazidime-avibactam, Ceftolozanetazobactam

Fourth-generation - Cefepime

“Fifth”-generation - Ceftaroline

27
Q

First Generation Cephalosprorins - drug names

A

Cefazolin*

Cephalexin*

Cefadroxil

28
Q

Second-generation Cephalosporins - drug names

A

Cefuroxime

Cefoxitin

Others - cefaclor, cefprozil, loracarbef, cefotetan

29
Q

Third - Generation Cephalosporins - drug names

A

Ceftriaxone

Cefotaxime

Cefdinir

Ceftazidime (alone or with avibactam or tazobactam)

others - ceftizoxime, cefpodoxime proxetil, cefditoren, ceftibuten, ceftixime

30
Q

Fourth - Generation Cephalosporins - drug names

A

Cefepime

31
Q

“Fifth”-generation Cephalosporins - drug names

A

Ceftaroline

32
Q

General Properties of Cephalosporins

A

given IM, IV or oral with poor CSF penetration unless meningeal inflammation (with some exceptions)

cross placenta and enters breast milk

renal excretion of unchanged drug

half life ranges from hour to 8 hours

33
Q

Ceftriaxone

A

third generation cephalosporin

biliary excretion

34
Q

1st Generation Cephalosporin Spectra of Activity and Uses

A

Gram-positive – MSSA and Streptococci
Gram-negative – PEcK (Proteus, E coli, Klebsiella) and respiratory bacteria

Uses - skin and soft tissue infections(s. pyogenes, MSSA), otitis media, GU tract infections

35
Q

cefazoline

A

1st generation cephalosporin - surgical propholaxis

36
Q

2nd Generation Cephalosporin Spectra of Activity and Uses

A

Streptococci and MSSA (staph)

Expanded gram-negative
HeNPEcK (H.influenzae & PEcK - Proteus, E coli, Klebsiella)

Cephamycins: B. fragilis

uses - Uncomplicated skin / soft tissue, respiratory, GU infection

37
Q

How is bacteroides fragilis treated?

A

resistant to all cephalosporins except:

cefoxitin and cefotetan (cephamycins)

38
Q

3rd Generation Cephalosporin Spectra of Activity and Uses

A

Activity of Penicillin G – useful for gram positive aerobes and anaerobes, N. meningitidis; H. influenzae; spirochetes

expanded gram negative spectrum

ceftazidime has anti-pseudomonas activity

39
Q

4th Generation Cephalosporin Spectra of Activity and Uses

A

Activity of Ampicillin

(Ampicillin is Pen G plus extended spectrum gram negative)

Extended spectrum gram negative + anti-pseudomonas

Uses - reserved for treatment of severe infections

40
Q

5th Generation Cephalosporin Spectra of Activity and Uses

A

Gram-positive aerobes and
anti-MRSA with the gram negative activity of ceftriaxone (gram negative bacilli, some enterobaster, H. influenza, and Moraxella catarrhalis.)

Uses - Skin/skin structure infections (including MRSA) and community-acquired pneumonia

41
Q

What are the cephalosporins that can penetrate into CSF without meningeal inflammation?

A

cefuroxime

cefotaxime

ceftriaxone

ceftazidime

42
Q

ceftriaxone

A

third generation cephalosporin

drug of choice for Gonorrhea and Lyme Disease infections

also can be used for s. pneumonia (penicillin-sensitive), MSSA, gram negative bacilli, some enterobaster, H. influenza, and Moraxella catarrhalis

43
Q

what drug options are available against Pseudomonas?

A

Piperacillin-tazobactam

Ceftaroline (5th Gen)

Cefepime (4th Gen)

ceftazidime (2nd Gen)

Carbapenems - except ertapenem

44
Q

What types of infections are cephalosporins not good for?

A

penicillin-resistact S. pneumoniae, MRSA, MRSE (with exceptions), enterococcus, listeria monocytogenes, C. Diff

KPC-producing enterobacteriacease, campylobacter jejuni, stenotrophomonas maltophillia, acinetobacter

atypicals – myoplasma, legionella pneumophila, chlamydia

45
Q

Adverse effects of 3rd-Generation Cephalosporins

A

I.M. painful injection; I.V. thrombophlebitis

Rare - renal tubular necrosis or interstitial nephritis

46
Q

Adverse effects of Ceftriaxone

A

(third gen)

biliary statis and cholestatic hepatitis

in neonates - hyperbilirubinemia (with potential kernicterus) and lung and kidkey damage from precipitation of Ca2+

(give cefotaxime to neonates instead)

47
Q

Adverse effects of Cefotetan

A

Hypoprothrombinemia by inhibition of Vit K activation

Disulfiram-like reaction (alcohol consumption)

48
Q

Carbapenems

A

Imipenem-cilastatin*
Meropenem*
Ertapenem*
Doripenem

49
Q

Characteristics and spectrum of Carbapenems

A

parentarel only, penetrates CSF
short half life

Broad Spectrum:
gram-positive and gram-negative, aerobic and anaerobic
Penicillin-resistant S. pneumonia
Penicillin-sensitive Enterococcus faecalis

Not affected by beta-lactamases but are suspectible to carbapenemases or metallo-β-lactamases (Klebsiella)

treatment of choice for:
− ESBL-expressing Enterobacteriaceae
− Pseudomonas aeruginosa, (may acquire resistance)
• except ertapenem
− Anaerobes, including B. fragilis
50
Q

Resistance to Carbapenems

A

Acquired

  • Class A serine protease - Klebsiella pneumoniase carbapenemase
  • Class B metallo-β-lactamases AKA carbapenemases

Intrinsic - MRSA, Enterococcus faecium, Clostridium difficile, Stenotrophomonas maltophilia

51
Q

what do carbapenemases do?

A

They hydrolyze penicillins, cephalosporins, and carpenems

They are not inhibited by beta-lactamase inhibitors

52
Q

Therapeutic uses of Carbapenems

A

Empiric treatment of serious infections of hospitalized patients who have already recieved beta-lactam therapy – lower respiratory, intra-abdominal, gynecological, skin, soft tissue, bone or joint infections

Intra-abdominal and pelvic infections caused by gram-positive bacteria, enterobacteriaceae and anaerobes

53
Q

Adverse effects of carbapenems

A

hypersensitivity reactions’
Common side effects

Seizures - greatest risk with imipenem and patients with renal insufficiency

hematologic - bleeding, agranulocytosis, leukopenia

GI - nausea, vomiting, diarrhea

C. diff superinfection

54
Q

Aztreonam - PK, Spectrum, Resistance

A

Monobactam - IV, IM; widely distributed; renal excretion

gram-negative aerobes only - esp. aerobic cocci and bacilli, including P. aeruginosa

Resistance:
• Gram-positive bacteria
• ESBLs; AmpC β-lactamase hydrolyze aztreonam
• Some strains of Enterobacteriaceae and Pseudomonas
(PBPs with low affinity for aztreonam)

55
Q

Therapeutic Uses of Aztreonam

A

Infections by susceptible gram-negative bacilli - UTI’s, LRT infections, septicemia, skin/skin structure infections, intra-abdominal infections, and gynecological infections

aztreonam inhalation - in Cystic Fibrosis Patients with Pseudomonas aeruginosa

Aztreonam should not be used alone for empiric therapy

56
Q

Adverse Effects of Aztreonam

A

cross-reactivity with beta-lactams is limited, so hypersensitivity reactions are less common
- Exception, ceftazidime

Nausea/vomiting/diarrhea

Thrombophlebitis and pain at injection site

C. difficile superinfection reported - and can occur more than two months after treatment

57
Q

Vancomycin - MOA and PK

A

glycopeptide - inhibit
peptidoglycan polymerization - D-ala-D-ala

poor absorption from gut so oral is only for local gut action,

IV for systemic with slow infusion bc of red man syndrome

only penetrates CSF with meningeal inflammation

6 hours half life, 24-h AUC/MIC and bacteriocidal

(efficacy depends on the total amount of drug given in a 24 hour period)

58
Q

Vancomycin - spectrum

A

Gram-positive pathogens only - Penicillin-resistant S. pneumoniae, MRSA and MRSE

Enterococcus faecalis and E. faecium - bacteriostatic

59
Q

Clinical Uses of vancomycin

A

MRSA / MRSE infections- - bacteremia, pneumonia, empyema, endocarditis, osteomyelitis, soft-tissue abscess

Penicillin-resistant streptococcal and enterococcal infections - endocarditis and necrotizing fascitis

meningitis due to penicillin resistant s. pneumoniae

C. diff infection - first line (before it was metronidazole)

Gram-positive infections in penicillin-allergic patients

60
Q

Vancomycin Cautions - AEs and DIs

A

Adverse Effects - red man syndrome (thought to be caused by direct release of histamine and not immunologic), hypersensitivity, phlebitis, ototoxicity and nephrotoxcity

Ototoxicity and nephrotoxicity are especially common when given with aminoglycosides

NSAIDs may increase serum levels of vancomycin

61
Q

Daptomycin

A

Cyclic lipopeptide with poor absorption, given IV only - forms a pore in the bacterial membrane causing loss of membrane pot. and cell death

Inactivated by pulmonary surfactant

half life - 8/9hrs

bacteriocidal, AUC/MIC – Efficacy correlates with total drug exposure to MIC ratio

62
Q

Daptomycin spectrum and therapeutic uses

A

all gram-positive pathogens – aerobic, facultative, and anaerobic

Effective against MRSA, MRSE, VISA, VRSA, and VRE

treatment of complicated skin and soft tissue infections, bacteremia, and VRE right-sided endocarditis

63
Q

What are the limitations of Daptomyicin

A

infections by gram-neg organism - ineffective

left-sided endocarditis and pneumonia - because inactivated by pulmonary surfactant

64
Q

Daptomycin Cautions

A

myopathy - monitor CK levels

Eosinophilic pneumonia - important to monitor, happens 2 to 4 weeks post-therapy

peripheral neuropathy

pregnancy category b, excreted in breast milk

not known to be safe in pediatrics

interacts with statins (HMG-CoA reductase inhibitors)

Pharmacology (23 decks)

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