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Module II > Cell Wall Synthesis Inhibitors > Flashcards

Cell Wall Synthesis Inhibitors Flashcards

1
Q

Beta Lactam structure

A

Thiazolidine ring attached to a B lactam ring that carries a secondary amino group

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2
Q

Pencillin MOA

A

PCN is a natural analog of D-ala-D-ala. PCD binding proteins (PBP’s) enzymes that remove terminal alanine to crosslink with neighboring peptide
PCDs inhibit this transpeptidation by covalently binding to PBP’s, blocking transpeptidation and inhibiting peptidoglycan synthesis within the bacterial cell wall
Leads to bacterial cell lysis and death
Bactericidal

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3
Q

Classes of PCN

A

Natural PCN
B lactamase resistant PCNs
Extended spectrum: amino-penicillins
Extended Spectrum: antipseudomomal penicillins

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4
Q

Natural penicillins

A

Penicillin G

Penicillin V

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5
Q

B-lactamase resistant penicillins

A

Methicillin
Nafcillin
Oxacillin
Dicloxacillin

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6
Q

Extended spectrum: amino-penicillins

A

Ampicillin

Amoxicillin

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7
Q

Extended spectrum antipseudomomal penicillin

A

Carbenicillin
Ticarcillin
Piperacillin

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8
Q

Penicillin G

A

natural PCN
Na or K
IV

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9
Q

Penicillin V

A

natural penicillin

PO

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10
Q

Benzathine Penicillin G

A

natural PCN

IM-long acting

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11
Q

Natural PCN spectrum of activity

A

streptococci, neisseria meningitidis, treponema pallidum, enterococcus faecalis.

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12
Q

Penicillinase-resistant Penicillins (penase-stable penicillins)

A

Methicillin (prototype)
Dicloxacillin (PO)
Nafcillin (im, IV, po)

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13
Q

Penicillinase resistant PCN spectrum of action

A 
s. aureus, staph epidermidis, penicillinase producing, streptococci but NOT:
MRSA
MRSE
Enterocci
Gram - organisms
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14
Q

Aminopenicillins

A

Extended spectrum. Includes:
Ampicillin (PO, IV, IM)
Amoxicillin (PO)
Spectrum: Gram +, streptococci, enterococcus faecalis, listeria monoctytogenes, treponema pallidum. Extended gram -: h. flu, some ecoli and proteus mirabilis.
NOT: klebsiella, pseudomonas, little staph coverage, NOT MRSA, MRSE

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15
Q

Antipseudomonal PCNs

A

extended spectrum.
Carboxypenicillins: Carbenicillin (PO) and Ticarcillin (IM, IV)
Ureidopencillins: Piperacillin
Spectrum: Expanded gram - to include p. aeruginosa, E. coli, serratia, proteus mirabilis and enterobacter, kelbsiella pneumonia. Gram +: streptococci, not as good as PCN. Poor staph, NOT MRS, NOT good for enterococci

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16
Q

Penicillin Resistance

A
  1. Inactivation of B lactamases
  2. Modification of target (PBP)
  3. Impaired Penetration
  4. Efflux
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17
Q

Inactivation of B-lactamase

A

Most common. B lactamase breaks a bond in the B lactam ring of PCN to disable the molecule. Bacteria with this enzyme can resis the effects of PCN and other B lactam antibodies

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18
Q

Alteration in target PCN binding proteins

A

Alteration in target PBPs. Reduced affinity-can overcome with very high concentrations. Resistance in one organism may result from replacements of its PBP with PBO from resistant organism. MRS; streptcoccus pneumoniae and enterococci-penicillin.

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19
Q

PCN resistance by impaired permeability

A

Permeability barrier preventing penetration of antibiotic-gram - organisms.
Can down regulate porins or not make
not so critical by itself; important with b-lactamase
efflux pump - gram - organisms

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20
Q

Penicillins Absorption

A

Natural PCN: oral–poor; PCN-V more acid stable. Parenteral: PCN G usually given IV. PCN G procaine needs to be cautioned with an allergy to procaine. Penicillin G benzathine–delay absorption, low serum level sustained >7 days, used for B hemolytic step and treponema pallidum
PCN-ase resistant: nafcillin poorly absorbed PO, usually given IV. Dicloxacillin: acid stable, given on an empty stomach.
Aminopenicillins: Amoxicillin PO, can be given with food. Ampicillin, food decreases rate and extend of absorption, usually only given IV
Anti-pseudomonal–carbenicillin PO. Others IV/IM

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21
Q

PCN Distribution

A

Protein binding: nafcillin 90%, PCN G 60%, others less
adequate distribution into MOST tissues and fluids; sputum and milk 3-15% of serum; eye, prostate poor.
Poor penetration into cerebrospinal fluid when BBB intact: both passive transport and active transport out of CSF along with other organic compounds
Poor entry into CSF, difficulty crossing BBB; hydrophilic and active transport out
“Adequate” CSF concentrations 3-5% penetration attained during inflammation
CSF: probenecid–inhibits transport out of CSF; uremia–organic cmpds accumulate in CSF compete for transport; can accumulate and cause seizures
All cross placenta; risk category B

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22
Q

PCN Elimination

A

Primarily renal for most, both glomerular filtration (10%) and tubular secretion (90%) (probenecid inhibits)
half-life < 1hr (except benzathine PCN)
severe renal insufficiency t½ up to 10 hrs
Significant non-renal elimination for a few agents, no adjustment in renal insufficiency:
Nafcillin: primarily biliary
Oxacillin, diclox, clox: both renal and biliary

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23
Q

PCN G Clinical Use

A

Infections caused by Streptococci (S pneumoniae, MIC < 0.1 mcg/ml, viridans group streptococci), including upper and lower respiratory infections (pneumonia), arthritis, endocarditis, septicemia, meningitis

  • *meningococcus meningitis
  • *Syphilis (Treponema pallidum - DOC for all stages and forms) **Oral anaerobes (peptococcus, peptostreptococcus) and clostridia
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24
Q

PCN V Clinical Uses

A

Strep pharyngitis

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25
Benzathine PCN Clinical use:
syphilis | Single injection to treat beta-hemolytic strep pharyngitis
26
Penicillinase-resistant PCN’s Clinical Use
Infections caused by Staph aureus or Staph epidermidis | NOT MRSA or MRSE, not enterococcal infections
27
Aminopenicillins Clinical Use
Used to tx otitis media, upper respiratory tract infections, sinusitis, meningitis Infections due to susceptible strains of Haemophilus influenzae, Proteus mirabilis, and E coli DOC for Strep Grp B, uncomplicated enterococcus UTI, Listeria monocytogenses (+AG) , Lyme disease Oral anaerobes
28
Antipseudomonal PCN’s Clinical Uses
For serious infections caused by Gr (-) bacteria: bacteremias, pneumonias, bone, skin, intra-abdominal, gynecologic, infections following burns and UTI due to organisms resistant to PCN-G and ampicillin, especially Pseudomonas aeruginosa
29
Benzathine PCN Dose
**Given IM
30
PCN G Dose
**Given IV
31
PCN V Dose
250 – 500mg PO bid, tid, qid | ** Given PO
32
Dicloxacillin
125 - 500mg q6h, PO*
33
Nafcillin Dose
1-2 gm q4-6h IV**
34
Amoxicillin dose
500mg q8h PO or 875mg q12h Peds: UD=usual dose: 40-45 mg/kg/d div q12h or q8h HD=high dose: 80-90 mg/kg/d div q12h or q8h raised because of strep resistance
35
Ampicillin dose
250-500 mg q6h PO; 1-2 gm q3-4hr IV
36
Piperacillin Dose
3-4gm IV q4-6h (12 gm/day for most organisms, but for Pseudomonas 18-24 gm/day
37
B-lactam inhibitors
Clavulanic acid, sulbactam, tazobactam No antimicrobial activity, acts as a bodyguard Inhibit many but not all bacterial betalactamases; protect hydrolysable PCN’s against inactivation by these enzymes Goal is to extend spectrum of activity for the companion beta lactame
38
Examples of B-lactam inhibitors
Fixed combos: Amoxicillin + Clavulanic acid 125 mg = Augmentin PO Ampicillin + Sulbactam = Unasyn (IV) Ticarcillin + Clavulanic acid 100mg = Timentin (IV) Piperacillin + Tazobactam = Zosyn (IV) ** Enhanced activity against beta-lactamases produced by s. aureus (Not MRSA), h. flu, e. coli, klebsiella pneumonia, n. gonorrhoeae, salmonella, shigella **Inhibit chromosomal B-lactamases: legionella, bacteroides, branhamella *no enhanced activity against AmpC B-lactamases
39
Spectrum of Action with B-lactamase inhibitor
expands coverage of parent PCN. good against s. aureus, staph epidermidis (NOT MRSA, MRSE), strep, ok for enterocci. proteus, e. coli, klebsiella penumoniae, h. flu, moraxella, catarrhalis NOT PSEUDOMONAS
40
Dosing with B lactamase inhibitor
Augmentin: 875/125 bid PO; 500/125 or 250/125 tid PO Zosyn: 2.25gm = Pip 2g, Tazo 250mg; 2.275 Pip 3g, Tazo 375mg; 4.5gm Pip = 4g, Tazo 500mg. Given IV q6h
41
Cephalosporins Classification/Spectrum of Action
More stable to beta-lactamase than PCN; produced by cephalosporium mold. MOA: like PCN
42
First Gen Cephalosporins
Cephalothin Cefazolin (Ancef, Kefzol) Parenteral; surg prophylaxis; skin infections not caused by MRSA Cephalexin (Keflex) Oral Cepharadine
43
Secondary Gen Cephalosporins
``` Cefaclor Cefuroxime Cefonicid Cefoxitin Cefotetan ```
44
Third Gen Cephalosporins
``` Ceftriaxone Cefotaxime Ceftzoxime Cefixime Cefdinir Ceftazidime Cefpodoxime Cefditoren ```
45
Fourth Gen Cephalosporins
Cefepime
46
MRSA Activity Cephalosporins
Ceftaroline
47
Cephalosporins First Gen Spectrum of Action
S. aureus, NOT MRSA, streptococci--aerobic and anaerobic; E. coli, K. pneumoniae, P. mirabilis Resistant: enterococci sp, MRSE< MRSA, p. aerugenosa, b fragilis
48
First Gen ceph clinical use
Cefazolin used for surgical prophylaxis | Cephalexin used for UTI, cellulitis, skin and soft tissue infections, mastitis
49
Second Gen Ceph Oral agents:
Cefaclor (ceclor) cefuroxime axetil (Ceftin) Cefprozil (Cefzil)
50
Secon Gen Ceph parental agents
Cefuroxime (Zinacef) Cefotetan (Cefotan) Cefoxitin (Mefoxin)
51
Second Gen Ceph spectrum of action
Most important: stretpcocci (aerobic and anaerobic) less than G1, but varies by drug; m. catarrhalis, klebsiella better than G1 Cefuroxime, cefaclor: h. flu but not serratia or b. fragilis Cefoxitin/cefotetan: bacteroides frafillis and some serratia, less against h. flu *NOT MRSA, MRSE, ENTEROCCI, P. AERUGENOSA
52
Second Gen Ceph clinical uses
PO for sinusitis, otitis media, LRI Surgical prophylaxis for "dirty" surgeries--GI, hysterectomy: cefoxitin, cefotetan Peritonitis or diverticulitis: cefoxitin, cefotetan
53
Third Gen Ceph oral agents
Cefixime (Suprax) Cefpodoxime (Vantin) Cefibuten (Cedax) Cefdinir (Omnicef)
54
Third Gen ceph parenteral agents
Ceftazidime (Fortaz) | Ceftriaxone (Recephin)
55
Third gen ceph B. fragilis group
Cefotaxime (Claforan) | Ceftrizoxime (Ceftizox)
56
Third gen ceph spectrum of action
Neisseria gonorrhea: ceftriaxone, cefixime expanded activity for most enterobacteriaceae (e. coli, klebsiella, serratia) p. aeruginosa--limited to ceftazidime ' PCN reistant streptococcus pneumoniae--ceftrixaone or cefotaxime some b. fragilis limited to ceftaxime *NOT enterococci sp, listeria, MRSA or MRSE
57
Third Gen ceph Clinical use
Respiratory, UTI, meningitis---crosses BBB Ceftriaxone 125mg IM or cefixime 400mg x 1 for n. gonorrhea pseudomonas infections serious infections in hospital patients intraabdominal infection
58
Fourth Gen ceph
Cefepime (Maxipime) -- parenteral
59
Fourth gen ceph spectrum of action
streptococci--better than G2, G3 Gram - organisms like G3 p. aeuruginosa like ceftazidime Resistant: enteroccia MRSA, MRSE, listeria monocytogenes
60
Fourth Gen ceph clinical use
like G3,, ? less effect on SPICE B-lactamase induction
61
Cefaroline (Teflaro)
New IV celphalosporin with activity against MRSA; other microbial coverage similar to ceftriaxone. MOA: binds to penicillin-binding proteins to inhibit cell wall synthesis; high affinity to PBP2a (encoded by MedA gene in MRSA) Use: skin and skin structure infections; not established for PNA tx.
62
Cephalosporins Pharmacokinetics
Distibution: Ceftazidime or cefepime are DOS for meningitis caused by pseudomonas. MICs are sufficiently low; CSF concentration are higher Elimination: Renally eliminated >7-% via active tubular secretion and GFR. EXCEPT ceftriaxone--biliary elimination T1/2 for most = 2 hrs except CEFTRIAXONE = 8 HOURS
63
Cephalosporin Dosing
IV: Cefazolin: 500 mg to 2 gm IV, IM q8h Ceftriaxone: 500mg-2g IV, IM w/ lido q24h Cefepime: 1-2g IV q12h PO: Cephalexin: 250-500mg q6hr or 500mg q12h
64
PCN and ceph hypersensativitiy
both usually tolerated well PCN hypersens most common--5-8%, but only 5-10% have reaction with reexposure Ceph: in pts w/ pcn, ~7%, w/o 1-2% 4 types of hypersensitivity "ampicillin rash" 9% of pts--not true allergy
65
Type I sensativity: IgE mediatied
Immediate: <1%, anaphylaxis Accelerated: 1-72 hrs, uticaria Avoid ceph in pts with recent h/o immediate reaction to PCN skin testing can help prevent or predict sensativity
66
Type II: cytotoxic IgM and IgG antibody mediated
hematologic +coombs test (3%) small # of pts develop hemolytic anemia
67
Type III: Immune complex of PCN and IgG or IgM
1-7% of patients Serum sickness (fever, malaise, uticaria) usually 6-10 days after start of PCN, 2nd, 3rd gen ceph
68
Type IV: T-cell mediated; delayed/late
48+ hours, dermatologic maculopapular rash | most common with PCN G
69
PCN and ceph ADRs
Diarrha (esp amp, amox, ceftriaxone, cefoperozone) IM-pain, sterile abscess, redness IV: phlebitis, pain, burning, redness Hepatitis: rare. *Pseudocholelithiasis (biliary sludging) – seen with ceftriaxone seizures--rare potassium load (PCN G) sodium load (ticarcillin) N-methyltetrazole ring--cefotetan antabuse reactions--MTT-containing cephs Jarisch-hexheimer reaction--PCN G with syphilis
70
PCN-ceph Drug interactions
Probenecid-blocks secretion at renal tubules Aminoglycosides-PCN Wafarin: dicloxacillin and nafcillin reduce warfarin effect, cephs with MTT side chain
71
Ceftaroline
Teflaro pharmacokinetics: primarily rental elimination half life=2.6 hours ADR: N/D, rash, coombs conversion Preg Cat B
72
Carbapenems Drugs
Imipenem/cilastatin (Primaxim) Meropenem (Merrem IV) Ertapenem (Invanz) Doripenem (Doribax)
73
Carbapenems Spectrom of Action
Gram +, Gram -, enterobacteria, p.aerginosa NOT ertapenem B fragilis
74
Carbapenem Resistance mechanisms
Porin loss | Carbapenemase
75
Carbapenem clinical use
Reserve for serious infections caused by resistant organisms UTI, septicemia, GYN infections, intra-abdominal High PCN resistant pneumococci and enterobacter
76
Carbapenem pharmacokinetics
Usually IV Wide distribution--inflamed meninges cilastatin inhibits renal dehydropeptidase--decreased hydrolzation of imipenem in kidney primarily renal; reduce dose in renal insufficiency
77
Carbapenem ADRs
hypersensativity reactions: rash, fever, pruritis, up to 50% cross sensativity with PCN (higher than cephs) seizures GI
78
Monobactam
Aztreonam (Azactam) IV (also IM and inhalation) | elimination is primarily renal
79
Monobactam spectrum of action
Aerobic Gram - Only | e. coli, klebsiella, p. mirabilis, serratia
80
Monobactam clinical use
in pts with renal insufficiency, pcn or ceph allergy. not thought to cross react hypersensativities use not well definied
81
Vancomycin MOA:
Glycopeptide; Binds to d-ala-d-ala in Stage 1, prevents further growth of peptidoglycan and cross-linking
82
Vancomycin resistance
modification of the D-ala-D-ala site; terminal D-ala replaced by D-lactate
83
Vancomycin SOA
Bacteriocidal for Gram + MRSA, c. diff NO Gram - activity
84
Vancomycin Pharmacokinetics
``` GIVE IV Not absorbed PO IM creates sterile abscess, not absorbed\ Elimination: renal--1/2=4-8 hours normal adjust dose in renal insufficiency ```
85
Vancomycin clinical use
Serious infections such as sepsis, endocarditis, MRSA, MRSE
86
Vanco ADRs
Red Man syndrome--histamine release--infuse slowly (1-2hrs) Sterile abscess with IM Ototoxicity--serum level >60 mcg/mL Nephrotoxicity
87
Vanco Dose
Adults: 15-20mg/kg/dose q8-12h | Desired levels: trough 15-20mcg/mL, peak 20-50
88
Daptomycin
(Cubicin) First cyclic lipopeptide antimicrobial agent Use: skin infections caused by s. auerus including MRSA and strep Excreted renally; reduce dose when CrCl <30ml/min q48 hours ADE: anemia, myopathy IV ONLY
89
Fosfomycin
Use: tx of uncomplicated UTI in women caused be e.coli or e. faecialis Mix 3gm in warm water
90
Bacitracin
Topical use only
91
Cycloserine
Use: TB
92
Ceftobiprole
new cephalosporin, MRSA coverage, dosed 8 hrs

Module II (4 decks)

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