Aminoglycosides

Question 1

Examples of aminoglycosides

Answer 1

Amikacin, gentamicin, neomycin sulfate, streptomycin, tobramycin.

Question 2

Aminoglycosides and which type of bacteria

Answer 2

All bactericidal & active against some Gram-positive & many Gram-negative organisms
~ Amikacin, gentamicin, & tobramycin also active against Pseudomonas aeruginosa;
~ streptomycin active against Mycobacterium tuberculosis & now almost entirely reserved for TB.

Question 3

aminoglycosides give by which form and why

Answer 3

are not absorbed from gut (although risk of absorption in IBD and liver failure) & MUST be given by injection for systemic infections

Question 4

Gentamicin as aminoglycosides

Answer 4

CHOICE in the UK
~ broad spectrum but inactive against anaerobes + poor activity against haemolytic streptococci & pneumococci.
~ When used for ‘blind’ therapy of undiagnosed serious infections usually given in conjunction with penicillin or metronidazole (or both).
~ used together with another antibiotic for tx of endocarditis.
~ Streptomycin may be used as alternative in gentamicin-resistant enterococcal endocarditis.

Question 5

Loading & maintenance doses of gentamicin

Answer 5

~ calculated using patient’s weight + renal function (e.g. using nomogram)
~ adjustments made according to serum-gentamicin concentrations. ~ High doses occasionally indicated for serious infections, especially in neonate or in immunocompromised.
~ Whenever possible tx not exceed 7 days.

Question 6

Tobramycin

Answer 6

~ similar activity to gentamicin but more active against Pseudomonas
~ also administered by nebuliser or by inhalation of powder on cyclical basis (28 days of tobramycin followed by 28-day tobramycin-free interval) for treatment of chronic pulmonary Pseudomonas aeruginosa infection in cystic fibrosis; however, resistance may develop & some patients do not respond to treatment

Question 7

Neomycin sulfate

Answer 7

~ too toxic for parenteral administration & only be used for infections of skin or mucous membranes or to reduce bacterial population of colon prior to bowel surgery or in hepatic failure.
~ Oral administration = lead to malabsorption
~ Small amounts absorbed from gut in patients with hepatic failure &, as these patients may also be uraemic, cumulation may occur with resultant ototoxicity