2. Aminoglycosides

Question 1

Examples of aminoglycosides and their spectrum of activity

Answer 1

Amikacin, gentamicin, neomycin sulfate, streptomycin and tobramcyin. Active against some gram-positive organisms and many gram-negative organisms.

It is not anaerobic.

Question 2

Aminolgycoside mechanism of action

Answer 2

Binds irreversibly to bacterial ribsomes so is bactericidal

Question 3

Aminoglycoside indications

Answer 3

Septicaemia, endocarditis, hospital acquired pneumonia. Also treats infections caused by pseudomonas aeurginosa.

As they are inactive against anaerobes, it is usually given with a penicillin or metronidazole in blind therapy

Question 4

Route of aminoglyosides

Answer 4

Aminoglycosides are not absorbed from the gut and therefore given by injection for systemic infection

Question 5

Streptomycin typical indication

Answer 5

Tuberculosis

Question 6

Tobramycin typical indication

Answer 6

Cystic fibrosis

Question 7

Gentamicin therapeutic range

Answer 7

5-10mg/L after a dose

<2mg/L before a dose

The therapeutic range is very narrow.
This is lower in endocarditis
(Post dose 3-5mg/L and <1mg/L before a dose).

Question 8

Gentamicin spectrum of activity

Answer 8

Inactive against anaerobes and has poor activity against haemolytic streptococci and pneumococci

Question 9

How is tobramycin administered

Answer 9

Nebuliser or inhalation of a powder on a cyclical Basies, e.g 28 days of therapy then 28 days without therapy

Question 10

Neomycin’s administration

Answer 10

Too toxic for parenteral administration therefore only used for infections of the skin or mucous membranes or prior bowel surgery or in hepatic failure

Question 11

How are aminoglycoside levels monitored?

Answer 11

Serum concentrations to prevent excessive and subtherapaeutic concentrations

Question 12

MHRA guidance surrounding aminoglycosides

Answer 12

Increased risk of deafness in patients with mitochondrial mutations (though mutations are rare). Genetic testing conducted on patients on long-term treatment. Continuous monitoring of renal and auditory function is needed.

MHRA have warned that some batches of aminoglycosides contain some amounts of histamine, which can cause an allergic reaction.

Question 13

What are you monitoring for in aminoglycosides?

The ear is in the shape of….

Answer 13

Nephrotoxcitiy, auditory and vestibular function (otoxicity).

Patients must report signs of hearing loss, tinnitus, or dizziness

Question 14

Warning signs in aminoglycosides

Answer 14

Hearing impairment, hearing disturbance

Question 15

Increased risk of nephrotoxicity when aminoglycosides are given with

Answer 15

ciclosporin, tacromilus, vancomycin

Question 16

Increased risk of otoxicity when aminoglycosides are given with…

Answer 16

loop diuretics, vancomycin

Question 17

Common side effects of aminoglycosides

Answer 17

reduced apetite, chest discomfort, cough, fever, dizziness

Question 18

Appropriateness of aminoglyosides in pregnancy

Answer 18

Aminoglyosides are unsuitable for use in pregnancy

Question 19

Types of dosing with Gentamicin

Answer 19

Doses based on weight or IDBW in obese patients

Once-daily - where a high dose is given once a day (avoided in severe renal impairment <20mlmin or endocarditis).

Multiple daily - when gentamicin is given in 2-3 divided dose in 24 hrs (monitored after 3-4 doses). Patients with renal impairment require more frequent and earlier monitoring.

Question 20

Actions to take with Gentamicin monitoring

Answer 20

If levels are high, 1 hour after a dose, reduce the next dose

If levels are high just before the next dose is due, lengthen the interval between doses

In patients with renal impairment, increase the dose interval.
Reduce the dose in patients with severe renal impairment

Question 21

Appropriateness of aminoglycosides in pregnancy

Answer 21

AVOID, if essential gentamicin can be given

Question 22

Aminoglycoside interactions

Answer 22

Increased risk of otoxicity if taken at the same time as other ototoxic drugs, e.g loop diuretics. Space the doses with by a long period as possible.

Increased risk of nephrotoxicity if taken at the same time as other nephrotoxic drugs, e.g methotrexate, NSAIDS, cyclosporin and tacromilus, vancomycin, plain chemotherapy