Aminoglycosides Flashcards
Name the five types of aminoglycosides
Amikacin, gentamicin, neomycin sulfate, streptomycin and tobramycin
Bactericidal or bacteriostatic
Bactericidal
G+ or G-
Some G+ and many G-
Which aminoglycosides act against pseudomonas aeruginosa
Amikacin, gentamicin, tobramycin
What aminoglycoside acts against mycobacterium TB
Streptomycin
What aminoglycoside is normally the one of choice?
Gentamicin
How are LD and MD calculated for gentamicin
Weight and renal function, adjustments made according to serum gentamicin levels
MHRA alert for gentamicin
Histamine related reaction for some batches
When to measure gentamicin levels and what level should they be?
Standard daily dose regimen and endocarditis
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).
MHRA alert for aminoglycosides
Aminoglycosides (gentamicin, amikacin, tobramycin, and neomycin): increased risk of deafness in patients with mitochondrial mutations
CI for all aminoglycosides
Myasthenia Gravis (may impair neuromusclar function)
If trough level high what to do?
Increase dose intervals
If peak high what to do?
Reduce dose
Important side effects of aminoglycosides
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
Aminoglycosides and pregnancy + which one has greatest risk
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.
When MUST aminoglycoside concentrations be taken?
Obesity, if high doses are being given and in cystic fibrosis, elderly, renal impairment
What should be monitored during treatment
Renal function should be assessed before starting an aminoglycoside and during treatment.
Auditory and vestibular function should also be monitored during treatment.
When should a once-daily, high-dose regimen of an aminoglycoside be avoided?
In patients with a creatinine clearance less than 20 mL/ minute.
Parenteral treatment of an aminoglycoside should not exceed
7 days
If possible, what should be corrected before starting aminoglycoside treatment?
Dehydration
How are doses in obese people calculated
IBW
Which aminoglycoside is considered too toxic for systemic use?
Neomycin
Which class of drugs should you avoid with aminoglycosides
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.
Which aminoglycoside is more stable than gentamicin in terms of enzyme inactivation
Amikacin
What administration regimen is most appropriate for aminoglycosides and why?
OD - more convenient, provides adequate serum concentrations, and in many cases has largely superseded multiple-daily dose regimen
When should once daily regimens be avoided?
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.
Why can aminoglycosides not be given orally?
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.
Which aminoglycoside can be nebulised and for what condition?
Tobramycin - often used for 28 day cycles in CF
