Aminoglycosides

Question 1

Name the five types of aminoglycosides

Answer 1

Amikacin, gentamicin, neomycin sulfate, streptomycin and tobramycin

Question 2

Bactericidal or bacteriostatic

Answer 2

Bactericidal

Question 3

G+ or G-

Answer 3

Some G+ and many G-

Question 4

Which aminoglycosides act against pseudomonas aeruginosa

Answer 4

Amikacin, gentamicin, tobramycin

Question 5

What aminoglycoside acts against mycobacterium TB

Answer 5

Streptomycin

Question 6

What aminoglycoside is normally the one of choice?

Answer 6

Gentamicin

Question 7

How are LD and MD calculated for gentamicin

Answer 7

Weight and renal function, adjustments made according to serum gentamicin levels

Question 8

MHRA alert for gentamicin

Answer 8

Histamine related reaction for some batches

Question 9

When to measure gentamicin levels and what level should they be?

Standard daily dose regimen and endocarditis

Answer 9

For multiple daily dose regimen, one-hour (‘peak’) serum concentration should be 5–10 mg/litre; pre-dose (‘trough’) concentration should be less than 2 mg/litre.

For multiple daily dose regimen in endocarditis, one-hour (‘peak’) serum concentration should be 3–5 mg/litre; pre-dose (‘trough’) concentration should be less than 1 mg/litre. Serum-gentamicin concentration should be measured after 3 or 4 doses, then at least every 3 days and after a dose change (more frequently in renal impairment).

Question 10

MHRA alert for aminoglycosides

Answer 10

Aminoglycosides (gentamicin, amikacin, tobramycin, and neomycin): increased risk of deafness in patients with mitochondrial mutations

Question 11

CI for all aminoglycosides

Answer 11

Myasthenia Gravis (may impair neuromusclar function)

Question 12

If trough level high what to do?

Answer 12

Increase dose intervals

Question 13

If peak high what to do?

Answer 13

Reduce dose

Question 14

Important side effects of aminoglycosides

Answer 14

Ototoxicity and nephrotoxicity.

Nephrotoxicity occurs most commonly in patients with renal impairment, who may require reduced doses; monitoring is particularly important in the elderly.

Hypocalcaemia, hypokalaemia and hypomagnesaemia

Question 15

Aminoglycosides and pregnancy + which one has greatest risk

Answer 15

There is a risk of auditory or vestibular nerve damage in the infant when aminoglycosides are used in the second and third trimesters of pregnancy. The risk is greatest with streptomycin. The risk is probably very small with gentamicin and tobramycin, but their use should be avoided unless essential.

Question 16

When MUST aminoglycoside concentrations be taken?

Answer 16

Obesity, if high doses are being given and in cystic fibrosis, elderly, renal impairment

Question 17

What should be monitored during treatment

Answer 17

Renal function should be assessed before starting an aminoglycoside and during treatment.

Auditory and vestibular function should also be monitored during treatment.

Question 18

When should a once-daily, high-dose regimen of an aminoglycoside be avoided?

Answer 18

In patients with a creatinine clearance less than 20 mL/ minute.

Question 19

Parenteral treatment of an aminoglycoside should not exceed

Answer 19

7 days

Question 20

If possible, what should be corrected before starting aminoglycoside treatment?

Answer 20

Dehydration

Question 21

How are doses in obese people calculated

Answer 21

IBW

Question 22

Which aminoglycoside is considered too toxic for systemic use?

Answer 22

Neomycin

Question 23

Which class of drugs should you avoid with aminoglycosides

Answer 23

Loop diuretics - Both furosemide and gentamicin can increase the risk of ototoxicity.
Furosemide increases the risk of nephrotoxicity when given with gentamicin. Manufacturer advises avoid.

Question 24

Which aminoglycoside is more stable than gentamicin in terms of enzyme inactivation

Answer 24

Amikacin

Question 25

What administration regimen is most appropriate for aminoglycosides and why?

Answer 25

OD - more convenient, provides adequate serum concentrations, and in many cases has largely superseded multiple-daily dose regimen

Question 26

When should once daily regimens be avoided?

Answer 26

Endocarditis due to Gram-positive bacteria, HACEK endocarditis, burns of more than 20% of the total body surface area, or creatinine clearance less than 20 mL/minute.

Question 27

Why can aminoglycosides not be given orally?

Answer 27

Not absorbed from the gut (although there is a risk of absorption in inflammatory bowel disease and liver failure) and must therefore be given by injection for systemic infections.

Question 28

Which aminoglycoside can be nebulised and for what condition?

Answer 28

Tobramycin - often used for 28 day cycles in CF