gentamicin Flashcards
ahminoglycosides are primarily excreted …. so impairment has this consequence…
renally
so accumulation can occur in RI - increased risk of ototoxicity and nephrotoxicity
in which patients must you frequently monitor serum-amino glycoside conc
in pt with RI
monitoring of patients parameters (3)
assess renal function BEFORE starting and DURING treatment
monitor auditory and vestibular function DURING treatment
MHRA for all aminoglycosied by injection and when used by ear - increased risk of deafness in pt with mitochonridal mutations
- rare
- consider genetic testing esp in pt needing recurrent or long term treatment, however do not delay urgent treatment
- monitor renal and auditory function and hepatic and laboratory parameters to minimise risk of adverse effects
- pt with known mitochondrial mutations or FHx ototoxicity to inform Dr or pharmacist before using ahminoglycosides
there is an increased risk of ….. in pt with …. mutations
deafness with mitochondrial mutations (even if serum levels are within recommended range)
gentamicin MHRA advice about potential for histamine related adverse drug with IM, intrathecal or IV use
some batches of gentamicin sulphate API used to manufacture gentamicin may contain higher than expected levels of histamine (residual from manufacturing process)
monitor pt with signs of histamine related adverse reactions
particular caution required in pt taking concomitant drugs known to cause histamine release, in children and in pt with severe RI
some batches of gentamicin may contain higher than expected levels of histamine. thus you need to be aware of signs of histamine related adverse reactions e.g.
allergy symptoms
severe - anaphylaxis
some batches of gentamicin may contain higher than expected levels of histamine. thus you need to be aware of signs of histamine related adverse reactions. particular caution is requires in the following patients
patients taking concomitant drugs known to cause histamine release, in children, and in patients with severe renal impairment.
contraindications for all ahminoglycosides by injection and why
Myasthenia gravis (aminoglycosides may impair neuromuscular transmission)
why is it myasthenia gravis contraindicated for all aminoglycoses by injection
AG may impair neuromuscular transmission
whenever possible parenteral treatment should not exceed …
7days
what are two important side effects to consider with aminoglycoside therapy and who do they most commonly affect?
Ototoxicity and nephrotoxicity
Nephrotoxicity occurs most commonly in patients with renal impairment, who may require reduced doses; monitoring is particularly important in the elderly.
therapeutic drug monitoring of gentamicin with IM or IV use in adults. for multiple daily dose regimen, one hour peak serum conc should be ….. and pre-dose (trough) conc should be …..
one-hour (‘peak’) serum concentration should be 5–10 mg/litre;
pre-dose (‘trough’) concentration should be less than 2 mg/litre.
therapeutic drug monitoring of gentamicin with IM or IV use in adults. For multiple daily dose regimen in endocarditis, one-hour (‘peak’) serum concentration should be …. and pre dose (trough) conc should be ….
one-hour (‘peak’) serum concentration should be 3–5 mg/litre
pre-dose (‘trough’) concentration should be less than 1 mg/litre.
for multiple daily dose regimen in endocarditis, how often should you measure serum-gentamicin conc?
After 3 or 4 doses, then at least every 3 days and after a dose change (more frequently in renal impairment).
therapeutic drug monitoring of gentamicin - serum amino glycoside conc should be measured in all pt receiving parenteral aminoglycosides and MUST be determined in the following pt (3)
- obesity
- high doses being given
- CF
do you need to determine serum aminoglycoside concentrations in the elderly
MUST
in patients with normal renal function, how often should you measure serum AG conc?
after 3-4 doses of a multiple daily dose regimen
and after dose change
in adults, WHEN (not how often) should you take blood samples of serum AG conc for multiple daily dose regimens
- to get peak conc: take blood samples ~1h after IM or IV admin
- to get trough conc: take blood samples just before next dose is due
what to do in adults if pre-dose (though) is high and post dose (peak) conc is high
If the pre-dose (‘trough’) concentration is high, the interval between doses must be increased.
If the post-dose (‘peak’) concentration is high, the dose must be decreased.
can you use AG in pregnancy. when is risk of SE most likely? which drug is it most likely with and which drugs it is least likely with? monitoring requirements?
- risk of auditory of vestibular nerve damage in infant when used in 2nd and 3rd trimesters
- risk is greater with streptomycin
- risk is probably small with gentamicin and tobramycin but their use should be avoided unless essential
- if given in pregnancy, serum-AG conc monitoring is essential!
risk of auditory or vestibular nerve damage in the infant with AG are used in 2nd and 3rd trimesters of pregnancy. risk is greatest with this drug … and the risk if probably very small with these drugs …… but their use should be avoided unless essential
greatest risk with streptomycin
probably low risk with gentamicin and tobramycin
for streptomycin, side effects increase after a cumulative dose of …..g which should only be exceeded in exceptional circumstances
100g
streptomycin : one hour (peak) conc should be …. and the pre dose (trough) concentration should be …. (and in RI and in those over 50)
One-hour (‘peak’) concentration should be 15–40 mg/litre
Pre-dose (‘trough’) concentration should be less than 5 mg/litre (less than 1 mg/litre in renal impairment or in those over 50 years).
would you use ideal weight or actual weight for obese pt to calculate parenteral dose? and what do you do about monitoring
To avoid excessive dosage in obese patients, use ideal weight for height to calculate parenteral dose and monitor serum-tobramycin concentration closely.
WITH IM OR IV USE
tobramycin - monitor concentrations in pt with known or suspected signs of auditory dysfunction. if ototoxicity develops, discontinue until
until serum concentration falls below 2 mg/litre.
gentamicin has broad spectrum but is inactive against
anaerobes
when gentamicin is used as blind therapy of undiagnosed serious infections it is usually given in conjunction with…
a penicillin or metronidazole or both
a patient has gentamicin resistant enteroccal endocarditis. which AG do you give instead
streptomycin
MOA of AG
inhibit protein synthesis by binding to 30S ribosomal subunit
Are AGs bacteriostatic or bactericidal
BACTERICIDAL - they inhibit protein synthesis by binding to 30s ribosomal subunit and therefore kill the bacteria
in children and adults with normal renal function, AG conc should be measured when?
after 3 or 4 doses of a multiple daily dose regimen AND after a dose change
for multiple daily dose regimens for all AG in adults, when should blood samples be taken (with regards to the dose)
take ~1h after IM or IV admin (peak conc)
and just before the next dose (trough)
gentamicin - what to do in the following situations
1) trough too high
2) peak too high
3) RI
4) severe RI
1) increase dose interval
2) reduce dose
3) increase dose interval
4) also reduce dose
Gentamicin is ototoxic. name some other drugs that are also ototoxic and thus should be preferably avoided
cisplatin
loop diuretics
vancomycin
vinka alkaloids
serum AG conc levels always need to be determined in the following (4)
obesity
elderly
high doses
CF
what electrolyte disturbances can aminoglycosides cause
hypoMg and hypoCa
