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Cell Wall Synthesis Inhibitors Flashcards

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1
Q

What is the classification of Penicillin G?

A

penicillin
bactericidal
beta-lactam antibiotic

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2
Q

What is the mechanism of action of Penicillin G?

A

Cell wall synthesis inhibition - Inhibits transpeptidase enzyme which leads to the disruption of peptidoglycan (cell wall) synthesis, these defects in the cell wall leads to rupturing.

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3
Q

What is the spectrum of activity of Penicillin G?

A

narrow

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4
Q

What are the therapeutic indications of Penicillin G? (6)

A
  • G+ cocci - tonsillitis, Pneumococci
  • G- cocci – meningitis, gonorrhoea
  • G+ bacilli/rod - tetanus, gangrene
  • Bacteroides fragilis (oropharyngeal infections)
  • Treponema (syphilis)
  • Actinomyces (abscesses)
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5
Q

Why can Penicillin G not be administered orally?

A

It is acid labile (inactivated by gastric acid) which causes it to have a poor absorption in the GIT

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6
Q

How is Penicillin G administered?

A

intramuscular (IM) and intravenous (IV)

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7
Q

What % of Penicillin G is bound to plasma proteins?

A

50-60%

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8
Q

What is the T1/2 of Penicillin G and how does this affect excretion

A

Short (30 mins), so rapidly eliminated unchanged via kidneys

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9
Q

In which 3 ways can the effect of Penicillin G be prolonged?

A
  • Higher doses
  • Combined with probenecid
  • IM administration in depot form
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10
Q

What are 3 Disadvantages of Penicillin G?

A
  • Narrow spectrum of action
  • Acid-labile (so only parental administration)
  • beta-lactamase sensitive (inactivated by bacterial enzymes)
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11
Q

What are the 2 major adverse effects of Penicillin G?

A

Hypersensitivity reaction and Neurotoxic effects (convulsions)

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12
Q

What is the classification of Penicillin V

A

beta-lactam antibiotic

penicillin

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13
Q

What is the mechanism of action of Penicillin V?

A

Cell wall synthesis inhibition

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14
Q

What is the spectrum of activity of Penicillin V?

A

narrow

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15
Q

What are the therapeutic indications of Penicillin V?

A
  • less severe infections

- follow-up antibiotic after successful parenteral treatment of severe infections

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16
Q

How is Penicillin V administered?

A

orally (acid stable)

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17
Q

How is the % of Penicillin V oral-dose that is absorbed impaired?

A

impaired by food intake

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18
Q

What is the half-life of Penicillin V?

A

30min

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19
Q

What % of Penicillin V is bound to plasma proteins?

A

80%

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20
Q

Where is Penicillin V metabolised?

A

liver

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21
Q

By which organ is unchanged Penicillin V excreted?

A

kidneys

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22
Q

What are the adverse effects of Penicillin V?

A

Similar to Penicillin G

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23
Q

What is the classification of Cloxacillin/ Flucloxacillin?

A

beta-lactam antibiotic
Isoxazolyl penicillin
semisynthetic penicillin

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24
Q

What is the mechanism of action of Cloxacillin/ Flucloxacillin?

A

Cell wall synthesis inhibition

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25
What are the therapeutic indications of Cloxacillin/ Flucloxacillin?
They are sensitive to beta-lactamase- resistant isolates of S aureus (normally resistant to Penicillin G)
26
How is Cloxacillin/ Flucloxacillin administered?
Orally (acid stable), otherwise IM and IV
27
How is the % of Cloxacillin/ Flucloxacillin oral-dose that is absorbed impaired?
impaired by food intake
28
What is the half-life of Cloxacillin/ Flucloxacillin?
30-60min
29
By which organ is Cloxacillin/ Flucloxacillin excreted?
kidneys
30
What are the adverse effects of Cloxacillin/ Flucloxacillin?
Similar to Penicillin G
31
What is the classification of Ampicillin?
beta-lactam antibiotic | aminopenicillin
32
What is the mechanism of action of Ampicillin?
Cell wall synthesis inhibition
33
What is the spectrum of activity of Ampicillin?
broad-spectrum of activity
34
What are the therapeutic indications of Ampicillin? (3)
- gram-positive bacteria - gram-negative cocci - gram-negative bacilli : H. influenzae, Salmonella, Shigella, Proteus mirabilis and Entamoeba coli.
35
How is Ampicillin administered?
orally (acid stable), also parentally
36
How is the % of Ampicillin that is absorbed impaired?
impaired with food intake
37
What % Ampicillin is bound to plasma proteins?
17-20%
38
What is the half-life of Ampicillin?
80min
39
Where is Ampicillin eliminated?
in the gall and urine
40
What are the adverse effects of Ampicillin?
- weak oral absorption causes more damage to GIT microflora and diarrhoea - Others similar to penicillin G
41
What is the classification of Amoxicillin?
beta-lactam antibiotic | aminopenicillin
42
What is the mechanism of action of Amoxicillin?
Cell wall synthesis inhibition
43
What is the spectrum of activity of Amoxicillin?
broad-spectrum of activity
44
What are the therapeutic indications of Amoxicillin?
Similar to that of ampicillin
45
How is Amoxicillin administered?
Oral (acid-stable), IV, IM very painful
46
What % of Amoxicillin is absorbed in the GIT?
85% (not impaired by food intake)
47
What is the half-life of Amoxicillin?
80min
48
What is the serum concentrations of Amoxicillin compares to Ampicillin?
2 1⁄2 times higher serum concentrations are reached
49
How does the dosage of Amoxicillin compare to Ampicillin?
A lower dose than for Ampicillin can be administered
50
Describe the distribution of Amoxicillin in the body fluids
A wide distribution in body fluids except for the cerebrospinal fluid
51
What % of Amoxicillin is bound to plasma proteins?
17-20%
52
Where is Amoxicillin metabolised?
liver
53
By which organ is unchanged Amoxicillin excreted?
Kidneys
54
What is Co-amoxiclav?
A combination of Amoxicillin and clavulanic acid
55
What does Clavulanic acid do beta-lactamase?
inactivates it
56
What is beta-lactamase?
An enzyme produced by bacteria that inactivate beta-lactam antibiotics (resistance)
57
Why is clavulanic acid added to Amoxicillin?
it protects the antibiotic against inactivation
58
What are the 4 adverse effects of Amoxicillin?
- GIT disturbances, nausea and vomiting - Hepatitis, cholestatic jaundice from clavulanic acid - Excreted in breast milk - Others similar to Ampicillin
59
What are the 4 Cephalosporins?
- Cephazolin (first gen) - Cefuroxime (second gen) - Ceftriaxone (third gen) - Cefepime (fourth gen)
60
What is the spectrum of activity of cephalosporins?
broad
61
What is the mechanism of action of cephalosporins?
Cell wall synthesis inhibition
62
What is the classification of Cephalosporins?
Beta-lactam antiobiotics | semisynthetic antibiotics
63
Which Cephalosporin is the most effective against gram-positive organisms?
First generation (Cephazolin)
64
What is the consequence of a cephalosporin that is more effective against gram-negative organisms ?
they are less effective against gram-positive infections
65
What is an advantageous property of cephalosporins?
They have a greater beta-lactamase stability (compared to penicillins)
66
What type of bacteria is resistant to all cephalosporins?
enterococci
67
What is the spectrum of activity of first gen cephalosporins? (2)
Streptococci, Staphylococcus aureus
68
What is the spectrum of activity of second gen cephalosporins? (5)
E.coli, Klebsiella, Proteus, Haemophilus influenzae, Moraxella catarrhalis
69
What is the spectrum of activity of third gen cephalosporins? (4)
Enterobacteriaceae, Neisseria gonorrhoeae, Staphylococcus aureus, Streptococcus pyogenes
70
What is the spectrum of activity of fourth gen cephalosporins? (3)
As for 3rd gen, Is more resistant against beta-lactamases, aerobic gram-negative bacilli
71
How are first gen cephalosporins administered?
orally
72
How are cephalosporins administered?
Parentally
73
Are cephalosporins acid stable or acid labile?
Acid stable
74
Describe the absorption of cephalosporins in the GIT?
poor absorption
75
What is the half-life of cephalosporins?
1 hour
76
What are the 2 main excretion methods of cephalosporins?
glomerular filtration and tubular secretion.
77
What are the adverse effects of cephalosporins?(3)
- Hypersensitivity reactions - Intolerance to alcohol - Bleeding disorders
78
What is the classification of Imipenem and Meropenem
Carbapenems | Beta-lactam antibiotics
79
What is the mechanism of action of carbapenems?
Cell wall synthesis inhibition
80
What is the spectrum of activity of carbapenems?
broad
81
What are the therapeutic indications of carbapenems? (4)
septicaemia, endocarditis, lower respiratory tract and genito- urinary tract infections
82
Can imipenem be absorbed orally?
no
83
How and where is imipenem metabolised?
Rapidly hydrolysed by dipeptidase in proximal renal tubule
84
What inhibits dipeptidase?
Cilastatin
85
What is formulated with imipenem and why?
Cilastatin, blocks renal metabolism and enhances its urinary concentration
86
What are the adverse effects of carbapenems?
Similar to those of other beta-lactam antibiotics, include hypersensitivity and GIT effects.
87
What is the classification of vancomycin?
glycopeptide antibiotic | bactericidal
88
What is the mechanism of action of vancomycin?
Cell wall synthesis inhibition
89
How does vancomycin inhibit cell wall synthesis?
Binds to peptidoglycan penta-peptide, this inhibits transglycosylation and prevents cross-linking of the peptidoglycan latticework, leads to rupturing of cell wall
90
What are the therapeutic indications of vancomycin? (3)
- Life-threatening infections - G+ infections caused by methicillin-resistant, beta-lactamase producing staphylococci and enterococci - Bowel inflammation (pseudomembranous colitis): Caused by Clostridium difficile (after antibiotic tx)
91
How is vancomycin administered?
IV (not absorbed after oral intake and IM administration is painful)
92
What is the half-life of vancomycin?
4 to 11 hours
93
How is vancomycin excreted?
unchanged in the urine by glomerular filtration
94
What are the adverse effects of vancomycin? (2)
- Fever and rash | - Rapid administration causes histamine release which leads to hypotension and flushing (“red-neck/red-man” syndrome)
95
What are the contraindications of vancomycin? (2)
- People with auditory abnormalities, causes ototoxicity | - Geriatric patient, causes renal toxicity

Principles of Therapy Core Drugs (8 decks)

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