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Pharma 3 > Penicillins, Cefalosporins > Flashcards

Penicillins, Cefalosporins Flashcards

1
Q

Background Information: Penicillins and Cefalosporins

A

Are inhibitors of cell wall therefore bactericidal

Are beta lactam ABs

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2
Q

Beta Lactam ABs

Drug Groups

A 
Penicillins
Cefalosporins
Carbapenems
Monobactams
Beta Lactamase Inhibitors
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3
Q

Chemistry of beta lactam ABs

A 
A ring
   in penicillin: thiazoline ring
   cefalosporins: dihydrothiazine ring
   carboxylic group attached to it: to form water sol/insol 
      complexes

B ring
respo for antobacterial effect
AA bound to it; variations here resp for pharmacolo diff

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4
Q

Bacterial Cell Wall Structure

A

G+
Plasma membrane surrounded by thick peptidoglycan
–> lipophilic drugs better

G-
Plasma membrane surrounded periplasmatic place and
thin peptidoglycan layer
Porin proteins ‘bind’ peptidoglycan with outer
membrane–> hydrophilic drugs better

Peptidogycan
Polysaccharide rich chain with cont 2 alternating sugars
N Acetylglucosamine and N Acetylmuramic Acid

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5
Q

Mode of Action

A

Beta Lactam ABs inhibit proteins: Penicillin Binding protein = transpeptidase
–> inhibit cross linkage step of cell wall synthesis

Conformation of beta lactam AB is similar to that of
D-Ananyl-D-Alanine
–> beta lactams bind to active site of transpeptidase:
enzyme opens lactam ring and acetylates itself–>
modification–> irreversible inhibition

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6
Q

Synthesis of Bacterial Cell Wall

A

Stage 1
Synth of precursor molecules; incl conversion L-Alanine
into D-Alanine
Good: selective toxicity. L Alanine is encoded in
humans

Stage 2
Polymerisation of precursor molecules

Stage 3
Cross Linkage of Peptidoglycan fibers
Done by PBP

Constant Remodelling
–> point of attack for ABs

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7
Q

Mechanism of Resistance

A

Presence of beta lactamases
PBP Mutation (ex MRSA)
G-: can’t cross outer membrane-> needs porins
Mutation in porin or efflux mechanism (pumps)

Atypical bacteria that don’t have peptidoglycan layer
Slowly growing bacteria that don’t constantly remodel
IC bacteria–> protected

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8
Q

When do Penicillins not work?

A

Cell Wall less pathogens
IC bacteria
Slowly growing bacteria

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9
Q

Penicillins

Drug Groups

A

Early Penicillins with rel narrow spectrum
Penicillinase resistant with narrow spectrum
Aminopenicillins with medium spectrum
Antipseudomonal penicillins

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10
Q

Early Penicillins with Rel Narrow Spectrum

Pharmacokinetics
Spectrum

A

Penicillin G
IV or IM (decomp in acidic environment; acid labile)
3-4x daily
Well distributed in body; can’t pass BBB
Excreted unchanged renally–> good for UTIs
1st choice for meningococcus meningits
(inflammation destroys BBB)

Penicillin V
Acid stable–> orally; food delays absorption
IV: form salt with Na or K
Well distributed; can’t pass BBB
Excreted unchanged via urine–> good for UTIs
via OAT and OATP
Better for tonsillitis and other upper resp infections

Mainly G+: staphy (resistance); strep; enterocooci
Some G-: neisseria gonorrhea: Pen G only
Some spirochetes (treponema pallidum)
Some anaerobes (clostridium)

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11
Q

Early Penicillins with Rel Narrow Spectrum

Indications

A 
Clostridium infections
Neisseria meningitides
Pneumococcus pneumoniae
Endocarditis (Strepto- or enterococci)
Osteomyelitis
Soft tissue infections
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12
Q

Penicillinase Resistant with Narrow Spectrum

A

Only ones not sensitive to beta lactamases
Used for screening; otherwise not really in use anymore

Incompletely absorbed from GIT; food counters absorp
Evenly distributed in body
Low penetration of BBB
Extensively bind to PP
Elimination: unchanged renally
Nafcillin and Oxacillin mainly eliminated in bile

Narrow spectrum; mainly G+

Used in staphy infections with penicillin resistance

Meticillin, Oxacillin , Cloxacillin, Nafcillin

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13
Q

Aminopenicillins with Medium Spectrum

A

Group mainly used nowadays

Orally; acid stable
Good absorption from GIT: Amoxicillin best
Distribute evenly; low BBB penetration
Eliminated unchanged via urine

Spectrum: have AA side chain: + charged–> can easily cross G- membrane via porins

G+: staphy, strept, entero
G-: neisseria, proteus, salmonella, E.Coli

Uses
   Upper and lower resp tract infections
   UTIs
   H. Pylori eradication (in combo)
   Oseomyelitis
   Soft tissue infections
   Enterococcus endocarditis
   Surgical prophylaxis

Ampicillin, Amoxicillin
Augmentin: Amoxicillin + clavulanic acid

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14
Q

Antipseudomonal Penicillins

A

Poor absorption from GIT; require parenteral admin
Distribute evenly throughout body; low BBB penetration
Eliminated unchanged via urine

Rel. ineffective against G+
G-: proteus, pseudomonas

Used 
   UTI
   Klebsiella infections
   Sepsis; endocarditis
   Hospital acquired pneumonia 
Carboxypenicillins: obsolete due to resistance
Ureidopenicillins
    Azlocillin
    Piperacillin (combo with tazobactam)
   Mezlocillin
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15
Q

Adverse Effects of Penicillins

A

Most common is HSR–> all four!
IgE–> anaphylaxis, angioedema
IgM and G–> vasculitis, neutropenia
Immune complex formation–> vasculitis, serum sickness
T Cell Med.–> Stevens Johnsons, urticaria
Reason: penicillins and breakdown products are haptens

Other
   Diarrhoea
   Decrease vit K--> inhibition of blood coagulation
   --> due to killing of gut flora
   Pseudomembranous colitis

Pseudoallergic Reaction: Measles like rash
Pseudo because no memory cells produced

High dose–> seizures; esp if kidney failure or meningitis +

Cross sensitivity

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16
Q

More fun facts: Penicillins

A

Practical strength >T1/2 due to irreversible inhibition

Some metabolised into penicilloic acid

17
Q

Postantibiotic Effect

A

Persistent suppression of bacterial growth

Short in G+
Absent in G-

18
Q

Cephalosporins

Drug Classification

A

1st - 4th Generation

19
Q

Cephalosporins

1st Generation

A

Cefalexin: orally as well absorbed from GIT

Cefazolin: parenteral as not well absorbed

Narrow spectrum
Mainly G+ such as staphylo or strepto
G- minor: proteus; E Coli

–> uses quite limited
Skin and soft tissue infections (prophylactic pre surg)
UTIs
Upper and lower resp infection

Special SE
   inhibition of 
     aldehyde dehydrogenase (inhib alcohol metab.)
         disulfiram like reaction
     vit K epoxide dehydrogenase
        coumarin like effects
20
Q

Cefalosporins

2nd Generation

A

G+: weaker than 1st gen
G-: broader: proteus, H. influenzae, E. Coli, Klebsiella
Some anaerobic bacteria

Good for gonorrhoea

Uses
Mainly upper resp tract infections
UTIs

Cefaclor (oral)
Cefuroxime (parenteral)
Cafamandol (also disulfiram and coumarin like effects)

21
Q

Cefalosporins

3rd Generation

A

Broad spectrum
Many G+s except MRSA
Many G-s
Many Anaerobics

Uses
   UTI and resp TI
   Soft tissue infections
   Cross BBB--> 1st choice for H. Influenzae Meningitis
   1st choice gonorrhoea (ceftiaxone)
   Antipseudomonal (ceftazidime)
Cefixime (oral)
Cefotaxime (parenteral)
Ceftriaxone (parenteral)=== GONORRHOEA
    biliary excretion in up to 40%; can clog up bile ducts in 
    kiddies
22
Q

Cefalosporins

4th Generation

A

Broad spectrum; similar to 3rd generation
Also good for MRSA (ceftobiprole)

Reserved for patients with life threatening infections by MDR

Cefepime
Cefpriome
Ceftobiprole
Ceftraroline 
All parenterally given
23
Q

Cefalosporins

SE

A

HSR; similar to that of penicillin
Show cross sensitivity
Biliary or uninary sludging–> stone formation
due to insoluble Ca complex formation by ceftriaxone
Nephrotoxic
Coumarin and Disulfiram like effects

Pharma 3 (14 decks)

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