C.13.Aminoglycosides

Question 1

In what case do we give monotherapy of Aminoglycosides?

Answer 1

pyelonephritis

in any other case–> given in combination

Question 2

mechanism of action of Aminoglycosides

Answer 2

binds to the 30s ribosomal subunit and interfere with protein synthesis by:

1. blocking formation of the initiation complex
2. inducing misreading of mRNA–>non-functional protein
3. inhibiting translocation

Question 3

what kind of killing action do aminoglycosides have?

Answer 3

concentration-dependent

Question 4

what kind of killing action do penicillins and cephalosporins have?

Answer 4

time-dependent

Question 5

are aminoglycosides bactericidal or bacteriostatic?

Answer 5

bactericidal

Question 6

toxicity of aminoglycosides is both concentration-dependent and..

Answer 6

time-dependent

Question 7

what does Post-antibiotic effect (PAE) mean?

Answer 7

killing action continues after plasma levels have declined below the MIC

Question 8

What does Concentration-dependent killing action mean?

Answer 8

the antibacterial effect is increased proportionally above the MIC

Question 9

What does time-dependent killing action mean?

Answer 9

independent of concentration, continuous as long as blood levels are maintained above the MIC

Question 10

What are the side effects of aminoglycosides? (5)

Answer 10

“NO TAN”
Nephrotoxicity
Ototoxicity

Teratogenicity –> fetal ototoxicity
Allergic skin reaction–> contact dermatitis
Neuromuscular blockade

Question 11

which Aminoglycoside has the broadest Spectrum? (least resistant)

Answer 11

Amikacin

Question 12

which aminoglycoside is too toxic for systemic use (injection)?

Answer 12

Neomycin

extremely nephrotoxic

Question 13

what is Paromomycin and what is it used for?

Answer 13

luminal-active agent

used against intestinal parasites (Entamoeba histolytica)

Question 14

list the Aminoglycosides

Answer 14

“Mean” (a”min”oglycoside) GNATS cannot kill anaerobes

Gentamicin 
Neomycin 
Amikacin 
Tobramycin 
Streptomycin 
*Netilmicin 
*Kanamycin 

nnot–> Nephrotoxicity, neuromuscular blockade
ototoxicity, teratogenicity

Question 15

what is the spectrum and clinical use of GNAT (Gentamycin, Netilmicin, Amikacin, Tobramycin)?

Answer 15

1. Aerobic gram - (E.coli, Enterobacter, Klebsiella, proteus, pseudomonas, Serratia)
2. in combination with β-lactam AB:
   - Enterococci (with penicillin)
   - Pseudomonas (with 3rd gen’ cephalosporin)

Question 16

what is the spectrum and clinical use of Streptomycin?

Answer 16

in combination with penicillin:
TB (2nd line agents), Tularemia, plague
Enterococcal endocarditis

Question 17

uses of Neomycin

Answer 17

used to suppress intestinal flora before bowel surgery (oral)
topical use–> ear infections (ear drops)

Question 18

what is Spectinomycin?

Answer 18

not an aminoglycoside but have similar mechanism

Question 19

what are the mechanisms of resistance of Aminoglycosides

Answer 19

1. plasmid-encoded inactivating enzymes (acetylation of the drug)
2. alteration of ribosomal binding site
3. intrinsic resistance of anaerobes - can’t penetrate the cell, requires O₂

Question 20

which aminoglycoside may be active against some gentamicin-resistant and tobramycin-resistant bacteria?

Answer 20

Netilmicin

Question 21

how are ‘GANTS’ given?

Answer 21

parenteral

Question 22

what is the T1/2 of ‘GANTS’?

Answer 22

2-3hours

Question 23

what type of elimination occurs in aminoglycosides

Answer 23

renal

directly proportional to creatinine clearance

Question 24

dosing regimens of Aminoglycosides?

Answer 24

2-3 times daily, or once