Infection: Aminoglycosides

Question 1

What are the five aminoglycoside drugs?

Answer 1

Amikacin
Gentamicin 
Neomycin 
Streptomycin
Tobramycin

Question 2

All aminoglycosides are what?

Answer 2

Bactericidal

Question 3

What is the spectrum of activity of aminoglycosides?

Answer 3

All are bactericidal and active against some Gram-positive and many Gram-negative organisms.

Question 4

Amikacin, gentamicin and tobramycin are active against what organism commonly seen in cystic fibrosis?

Answer 4

P.aeruginosa

Question 5

Streptomycin is used almost entirely for the treatment of what condition? why is this?

Answer 5

Tuberculosis as it is active against mycobacterium tuberculosis.

Question 6

Why are a aminoglycosides not given orally?

Answer 6

They are not absorbed from the gut (although there is a risk of absorption in IBS and liver failure) and must therefore be given by injection for systemic injections.

Question 7

What is the aminoglycoside of choice in the UK?

Answer 7

Gentamicin.

Question 8

What is the spectrum of activity of gentamicin?

Answer 8

Broad but inactive against anaerobes and poor activity against haemolytic streptococci and pneumococcie.

Question 9

What is gentamicin inactive against?

Answer 9

Anaerobes

Question 10

What does gentamicin have poor activity against?

Answer 10

Haemolytic streptococci and pneumococcie.

Question 11

When used for the ‘blind’ therapy of undiagnosed serious infections, gentamicin is usually given in conjuction with what?

Answer 11

Peniciilin or metronidazole (or both)

Question 12

What may be used as an alternative in gentamicin-resistant entorococcal endocarditis?

Answer 12

Streptomycin

Question 13

How are loading and maintenance doses of gentamicin calculated?

Answer 13

Patient weight and renal function (using a nomogram)

Question 14

Whenever possible, treatment length of gentamicin should not exceed what?

Answer 14

7 days.

Question 15

How is amikacin better than gentamicin?

Answer 15

it is more stable to enzyme inactivation.

Question 16

Amikacin is used in the treatment of what?

Answer 16

Serious infections caused by gentamicin-resistant Gram-negative bacilli.

Question 17

Tobramycin can be administered by nebuliser or by inhalation of powder on a cyclical basis (28 days of tobramycin followed by a 28-day tobramycin-free interval) in the treatment of what?

Answer 17

Chronic pulmonary Ps. aeruginosa infection in cystic fibrosis.

Question 18

Neomycin sulfate is only used for infections of the skin or mucous membranes or to reduce the bacterial population of the colon prior to bowel surgery why?

Answer 18

It is too toxic to be used via IV/parenteral.

Question 19

Aminoglycosides work by irrerversibly binding to what?

Answer 19

The 30s subunit of bacterial ribsomes

Question 20

Which of the following is false?

Aminoglycosides have long half-lifes.

Aminoglycosides are bactericidal.

Aminoglycosides may exacerbate weakness in patients with Myasthenia Gravis.

Answer 20

Aminoglycosides have short half-lives: between 1 and 4 hours.

Question 21

Aminoglycosides work best against:

Aerobic gram-negative
Anaerobic gram-negative
Aerobic gram-positive
Anaerobic gram-postive

Answer 21

Aminoglycosides are primarly effective against aerobic gram-negative bacteria such as Pseudomonas, Acinetobacter and Enterobacter.

Question 22

Aminoglycosides can cross which, if any, of the following:

The blood brain barrier.
The placenta.

Answer 22

Aminoglycosides can NOT cross the BBB.

However, they can cross the placenta and pose a risk to the fetus.

Question 23

Which aminoglycoside is most commonly used in the treatment of cystic fibrosis patients infected with Pseudomonas aeruginosa?

Gentamicin
Tobramycin
Neomycin
Streptomycin
Amikacin

Answer 23

Tobramycin may be delivered via the inhalational route, and is therefore frequently deployed in cystic fibrosis patients infected with pseudomonas aeruginosa.

Question 24

Aminogycosides are retained in which part of the renal system, which is what eventuates as renal damage over time?

Is this irreversible or reversible?

Answer 24

Reversible:

Proximal tubule.

Question 25

Why are aminoglycosides often administered alongside penicillins in the treatment of resistant infections?

Answer 25

Often, aminoglycosides cannot penetrate the cell wall due to resistant mechanisms. Taking penicllins - such as ampicillin - alongside aminoglycosides (particularl gentamicin) has become common because penicllins disrupt cell wall integrity.