CLASSES OF ABX: AMINOGLYCOSIDES Flashcards
Aminoglycoside examples
Amikacin
Gentamicin
Neomycin
Streptomycin
Tobramycin
MOA
- Irreversibly bind to 30s ribosomes
- Inhibit protein synthesis
What organisms are ahminoglycosides active against?
SOME Gram-POSITIVE
MANY Gram-NEGATIVE organisms.
What aminoglycosides are active against Pseudomonas aeruginosa?
Amikacin, gentamicin and tobramycin
How are AG administered
- via injection: OD or multiple (2-3 divided doses)
- not absorbed from the gut
Which AG is not administered via injection?
Neomycin
- too toxic
- PO/ topical
Which AG can be absorbed via nebuliser/ inhalation poweder?
Tobramycin
- via injection, nebuliser, inhalation powder
What aminoglycoside is active against Mycobacterium tuberculosis?
Streptomycin
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
Indication
- In combination therapy for:
o Endocarditis
o Septicaemia
o meningitis
o other CNS infections - biliary-tract infection
- prostatitis
- pneumonia.
Side effects
- OTO/NEPHROTOXICITY
- N+V
- AAC
- Peripheral neuropathy
- Electrolyte disturbances.
Contraindication
- Avoid in pregnancy
- Obese patients
- Avoid using in conjunction with ototoxic drugs
- Avoid using in conjunction with drugs that cause renal impairment
Contraindications for all ahminoglycosides by injection
Myasthenia gravis (aminoglycosides may impair neuromuscular transmission)
why is it myasthenia gravis contraindicated for all aminoglycosides by injection
AG may impair neuromuscular transmission
Aminoglycosides and pregnancy
- Auditory or vestibular nerve damage in 2nd and 3rd trimesters
- Greater risk with streptomycin
- Less risk with gentamicin and tobramycin but their use should be avoided unless essential
- Monitor serum conc if you do give it
Aminoglycosides and obese patients
o Use ideal body weight
o Based on height to calculate parenteral dose
What are examples of other ototoxic drugs
o e.g. cisplatin
o loop diuretics (furosemide, spironolactone, bumetanide, torasemide)
o vancomycin
o vinca alkaloids (vinblastine, vincristince, vindesine, vinfluine
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
elderly
How often should you monitor serum-aminoglycoside concentrations
- after 3 or 4 doses, then every 3 days
- after a dose change
When should you monitor renal function
Assess renal function BEFORE starting and DURING treatment
Monitor auditory and vestibular function DURING treatment
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
Multiple daily dose regimen (peak)
5-10mg/L
Multiple daily dose serum concentration (trough)
Less than or equal to 2mg/L
Multiple daily dose in endocarditis (peak)
3-5mg/L
Multiple daily dose in endocarditis (trough)
Less than 1mg/L
Multiple daily dose regimen
one-hour (‘peak’) serum concentration should be 5–10 mg/litre;
pre-dose (‘trough’) concentration should be less or equal too 2 mg/litre.
Multiple daily dose in endocarditis
one-hour (‘peak’) serum concentration should be 3–5 mg/litre
pre-dose (‘trough’) concentration should be less than 1 mg/litre.
Why is the dose lower in endocarditis
endocarditis is lower because we co-prescribe with other antibiotics
What do we do if the trough is too high?
Increase dose interval
What do we do if the peak is too high?
Decrease dose
What do we do if their is renal impairment?
Increase dose interval
What do we do in severe renal impairment?
Decrease dose
whenever possible parenteral treatment should not exceed …
7 days
Aminoglycosides for systemic infections
injections for systemic infections
neomycin is used to reduce bacterial population of the colon before bowel surgery or in hepatic failure
How are aminoglycosides primarily excreted?
Renally
SO accumulation can occur in RI - increased risk of ototoxicity and nephrotoxicity
What is the MHRA warning with regards to histamine and Gentamicin?
- Some batches of gentamicin may contain higher then expected histamine
- MHRA have asked to monitor for signs of histamine-related ADR’s in patients taking drugs known to increase histamine release or whom are severely renally impaired
What is the MHRA warning regarding
Aminoglycosides and mitochondrial mutations?
- Gentamicin, amikacin, tobramycin, and neomycin given by injection all increase risk of deafness in patients with mitochondrial mutations
- Gentamicin given by ear drops can also increase the risk
