Infection: Aminoglycosides Flashcards
What are the five aminoglycoside drugs?
Amikacin Gentamicin Neomycin Streptomycin Tobramycin
All aminoglycosides are what?
Bactericidal
What is the spectrum of activity of aminoglycosides?
All are bactericidal and active against some Gram-positive and many Gram-negative organisms.
Amikacin, gentamicin and tobramycin are active against what organism commonly seen in cystic fibrosis?
P.aeruginosa
Streptomycin is used almost entirely for the treatment of what condition? why is this?
Tuberculosis as it is active against mycobacterium tuberculosis.
Why are a aminoglycosides not given orally?
They are not absorbed from the gut (although there is a risk of absorption in IBS and liver failure) and must therefore be given by injection for systemic injections.
What is the aminoglycoside of choice in the UK?
Gentamicin.
What is the spectrum of activity of gentamicin?
Broad but inactive against anaerobes and poor activity against haemolytic streptococci and pneumococcie.
What is gentamicin inactive against?
Anaerobes
What does gentamicin have poor activity against?
Haemolytic streptococci and pneumococcie.
When used for the ‘blind’ therapy of undiagnosed serious infections, gentamicin is usually given in conjuction with what?
Peniciilin or metronidazole (or both)
What may be used as an alternative in gentamicin-resistant entorococcal endocarditis?
Streptomycin
How are loading and maintenance doses of gentamicin calculated?
Patient weight and renal function (using a nomogram)
Whenever possible, treatment length of gentamicin should not exceed what?
7 days.
How is amikacin better than gentamicin?
it is more stable to enzyme inactivation.
Amikacin is used in the treatment of what?
Serious infections caused by gentamicin-resistant Gram-negative bacilli.
Tobramycin can be administered by nebuliser or by inhalation of powder on a cyclical basis (28 days of tobramycin followed by a 28-day tobramycin-free interval) in the treatment of what?
Chronic pulmonary Ps. aeruginosa infection in cystic fibrosis.
Neomycin sulfate is only used for infections of the skin or mucous membranes or to reduce the bacterial population of the colon prior to bowel surgery why?
It is too toxic to be used via IV/parenteral.
Aminoglycosides work by irrerversibly binding to what?
The 30s subunit of bacterial ribsomes
Which of the following is false?
Aminoglycosides have long half-lifes.
Aminoglycosides are bactericidal.
Aminoglycosides may exacerbate weakness in patients with Myasthenia Gravis.
Aminoglycosides have short half-lives: between 1 and 4 hours.
Aminoglycosides work best against:
Aerobic gram-negative
Anaerobic gram-negative
Aerobic gram-positive
Anaerobic gram-postive
Aminoglycosides are primarly effective against aerobic gram-negative bacteria such as Pseudomonas, Acinetobacter and Enterobacter.
Aminoglycosides can cross which, if any, of the following:
The blood brain barrier.
The placenta.
Aminoglycosides can NOT cross the BBB.
However, they can cross the placenta and pose a risk to the fetus.
Which aminoglycoside is most commonly used in the treatment of cystic fibrosis patients infected with Pseudomonas aeruginosa?
Gentamicin Tobramycin Neomycin Streptomycin Amikacin
Tobramycin may be delivered via the inhalational route, and is therefore frequently deployed in cystic fibrosis patients infected with pseudomonas aeruginosa.
Aminogycosides are retained in which part of the renal system, which is what eventuates as renal damage over time?
Is this irreversible or reversible?
Reversible:
Proximal tubule.
Why are aminoglycosides often administered alongside penicillins in the treatment of resistant infections?
Often, aminoglycosides cannot penetrate the cell wall due to resistant mechanisms. Taking penicllins - such as ampicillin - alongside aminoglycosides (particularl gentamicin) has become common because penicllins disrupt cell wall integrity.
