Katzung 12th ed - Chapter 43 - Beta-lactams - Cephalosporins (1) Flashcards

1
Q

Give two examples of each generation of cephalosporin.

A

1st gen – Cefazolin, Cephalexin
2nd gen – Cefuroxime, Cefaclor
3rd gen – Ceftriaxone, Cefotaxime, Ceftazidime
4th gen – Cefepime

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2
Q

Describe the mechanism of action of cephalosporins.

A

It is the same as for penicillins. Cephalosporins bind to penicillin-binding proteins and inhibit transpeptidation in peptidoglycan synthesis. This inhibits the formation of cross-links in the cell wall that confer rigidity.

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3
Q

What is the difference in resistance mechanisms between penicillins and cephalosporins?

A

Cephalosporins are not as sensitive to beta-lactamases.

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4
Q

In addition to gram positive cocci, 1st generation cephalosporins are active against which bacteria?

A

E.coli, Klebsiella, Proteus.

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5
Q

It is important to note that 1st generation cephalosporins are NOT active against which bacteria?

A

Listeria, MRSA, Haemophilus, Pseudomonas, Enterobacter, Serratia, Citrobacter

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6
Q

What is the excretion method of 1st and 2nd generation cephalosporins?

A

Renal excretion. 10% by filtration, 90% by tubular secretion.

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7
Q

What is the half-life of cephalosporins: 1st gen? 2nd gen? 3rd gen?

A

1st gen: 30 minutes. Up to 10 hours in renal failure.
2nd gen: Variable.
3rd gen: 7-8 hours.

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8
Q

What is the route of metabolism and excretion for 3rd generation cephalosporins?

A

Metabolised by the liver and excreted in bile. Therefore there is no dosing adjustment required in renal failure.

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9
Q

What is the difference in microbial coverage of 1st generation and 2nd generation cephalosporins?

A

2nd generations cover the same as 1st, the only extra they cover is Haemophilus influenza and some Serratia.

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10
Q

Which cephalosporins can cross the blood-brain barrier?

A

3rd generations, and one of the 2nd generations (cefuroxime). Not 1st generations.

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11
Q

Which 3rd generation cephalosporin provides good coverage of pseudomonas?

A

Ceftazidime.

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12
Q

It is important to note that 3rd generation cephalosporins are NOT active against which bacteria?

A

Enterobacter and Listeria.

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13
Q

The 4th generation cephalosporins are useful against which bacteria? Which one are they still not quite useful for?

A

Useful for: Pseudomonas, Enterobacter, Haemophilus, Staph aureus, Neisseria.
Still under development: MRSA

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14
Q

The 4th generation cephalosporins: what is their route of clearance? Half-life?

A

Renally cleared. Half-life 2hrs.

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