Aminoglycosides Flashcards
List the 5 aminoglycoside drugs
Gentamicin Neomycin Amikacin Tobramycin Streptomycin
“Mean (aminoglycosides) GNATS caNNOT kill anaerobes”
List the anti-pseudomonal aminoglycosides
Amikacin, gentamicin, tobramycin
What is the spectrum of activity of aminoglycosides?
Active against most gram-negative and some gram-positive organisms
Which aminoglycoside can be used for the treatment of M.tuberculosis?
Streptomycin
Adult dose: 15 mg/kg daily (max per dose 1g) by deep IM injection, reduced in those under 50 kg and those over 40 years
**Treatment of TB with streptomycin is unlicensed and only indicated in TB which is resistant to other drug treatments
Which aminoglycoside is administered topically?
Neomycin
Indicated in the treatment of bacterial skin infections (think Neosporin)
Children and adults: apply 3 times a day for short-term use only
** Neomycin can also be administered orally as a means of treating hyperammonemia
What is the route of administration of aminoglycosides for treatment of systemic infections?
Injection (IM, slow IV injection, or IV infusion)
Aminoglycosides are not absorbed from the gut (except in some cases of IBD and liver failure) and must therefor be given by injection for systemic infections
**other preparations include creams, drops, and nebulised formulations for LOCALIZED infections
Can aminoglycosides be used to treat anaerobic infections?
No
Oxygen is required for active transport of aminoglycosides into bacterial cells
What are the indications for gentamicin? (16)
Gentamicin is the aminoglycoside of choice in the UK for the treatment of SERIOUS infections.
It has a broad spectrum BUT is inactive against anaerobes.
- Bacterial eye infections
- Bacterial otitis externa
- Moderate-severe diabetic foot infection
- Acute diverticulitis (in combination with amoxicillin and metronidazole)
- Leg ulcer infection (in combination with other drugs)
- Gram-positive bacterial endocarditis or HACEK endocarditis (in combination with other antibacterials)
- Septicemia
- Meningitis and other CNS infections
- Biliary-tract infections
- Pneumonia in hospitalized patients
- Adjunct to listeria meningitis
- Prostatitis
- Surgical prophylaxis
- Acute pyelonephritis
- Catheter-associated UTI
- Uncomplicated gonorrhea (in combination with azithromycin)
**ideal weight and height is used to calculate parenteral dose in obese patients to avoid toxicity; serum concentrations should be monitored closely
What is the main contraindication for all aminoglycosides? (1)
Myasthenia gravis
Aminoglycosides may impair neuromuscular transmission
What are the side effects of aminoglycosides?
NNOT
- nephrotoxicity (most commonly in patients with renal impairment (primarily renally excreted); may require reduced dose)
- neuromuscular blockade (contraindicated in MG)
- ototoxicity (vestibular AND cochlear systems; especially when used with loop diuretics or vancomycin)
- teratogenicity (deafness in newborns; used with caution in second and third trimester of pregnancy, especially streptomycin)
“Mean (aminoglycosides) GNATS caNNOT kill anaerobes”
**the main side-effects of aminoglycosides are dose-related, therefore care must be taken with dosage and monitoring (particularly in the elderly); whenever possible, parenteral treatment should NOT exceed 7 days; dehydration should be corrected before starting an aminoglycoside
List the indications for Amikacin (3)
Amikacin is indicated in SERIOUS gram-negative infections RESISTANT to gentamicin
- Acute prostatitis
- Acute pyelonephritis
- Catheter-associated UTI
List the indications for neomycin (3)
- Bacterial skin infections (topical; up to 3 times a day)
- Bowel sterilization before surgery (by mouth; 1g every hour for 4 hours, then 1g every 4 hours for 2-3 days)
- Hepatic coma (by mouth; up to 4g daily in divided doses usually 5-7 days)
List the indications for tobramycin (9)
(Similar to gentamicin)
- Severe eye infections
- Septicemia
- Meningitis and other CNS infections
- Biliary-tract infections
- Acute pyelonephritis
- Acute prostatitis
- Pneumonia in hospitalized patients
- UTI
- Chronic P.aeruginosa in patients with CF (inhalation of nebulised soln)
What are the main drug interactions with aminoglycosides? (5)
(Increased risk of ototoxicity when co-prescribed ~ vestibular or cochlear)
- Furosemide
- Vancomycin
(Increased risk of nephrotoxicity when co-prescribed)
- Cyclosporin
- Platinum chemotherapy
- Cephalosporins
- Vancomycin
What is the ballpark dosage when prescribing injected gentamicin?
- Dosing for once daily administration: 3-5 mg/kg in three divided doses to be given every 8 hours by IV infusion, slow IV injection (>3 min), or IM
- Dosing for multi-daily administration: initially 5-7 mg/kg with subsequent doses adjusted according to serum concentration
**use ideal body weight and height to calculate parenteral dose to avoid toxicity
Once daily administration of aminoglycosides is preferred to multi-daily dose regimens (2-3 divided doses during 24 hours) for convenience. However, a once-daily, high-dose regimen should be avoided in patients with gram-positive bacterial endocarditis, HACEK endocarditis, burns of more than 20% total body surface area, or creatinine clearance < 20mL/min (renally excreted).
Serum-aminoglycoside concentrations should be monitored in patients receiving parenteral aminoglycosides and must be determined in the elderly, in obesity, and in cystic fibrosis, or if high doses are being given, or if there is renal impairment.
