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Pharmacology > Aminoglycosides > Flashcards

Aminoglycosides Flashcards

1
Q

Serratia

A

Gentamicin

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2
Q

P. aeruginosa, Proteus

A

Tobramycin

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3
Q

Aminoglycosides - What Bacteria

A

Aerobic, Gram Negative

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4
Q

Aminoglycoside MOA

A

Bactericidal

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5
Q

Bacterial killing

A
  • Concentration-dependent

- Post-antibiotic effect

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6
Q

The higher the concentration,

the greater is the rate at which bacteria is killed.

A

Concentration-dependent

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7
Q

Is when residual bactericidal activity persist after serum conc. has fallen below MIC
(duration of this effect is conc.dependent)

A

Post-antibiotic effect

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8
Q

t/f

Greater efficacy when administered as a SINGLE LARGE DOSE than when given as multiple smaller doses

A

true

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9
Q

t/f
antibiotics that produce the:
longest PAEs
exhibit maximal PALEs

A

true

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10
Q

Active in alkaline/acidic ph?

A

Alkaline

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11
Q

Aminoglycosides are excreted rapidly in:

A

Kidneys

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12
Q

T/F

Aminoglycosides are Nphrotoxic and Ototoxic

A

True

Auditory and vestibular functions of CN VIII

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13
Q

AG is a Protein Synthesis Inhibitorthat acts where

A

ribosome level 30s

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14
Q

Distinguished by

A

2 or more Aminosugars linked to:

an aminocyclitol ring in central position (hexose nucleus)

by GLYCOSIDIC BONDS

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15
Q

Hexose ring

A

either streptidine

2-deoxystreptamine

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16
Q

where aminocyclitol is not central and contains streptidine instead of 2-deoxystreptamine

A

Streptomycin

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17
Q

What are the Aminoglycosides

A

Tobramycin, Amikacin, Netilmicin, Neomycin,

Gentamicin, Kanamycin, Streptomycin and Paromomycin

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18
Q

Induce LYSOSOMAL PHOSPHOLIPIDOSIS where?

A

in Proximal Tubule cells

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19
Q

interfere with mitochondrial functions

A

Produce ROS, deplete ATP

Several : induce site specific features of apoptosis

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20
Q

MOA

A

Diffuse

  • > aqueous channels (formed by porin proteins in outer mem. of G(-) bacteria)
  • > periplasmic space
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21
Q

depends on ELECTRON TRANSPORT

membrane elec. potential : interior negative

A

ENERGY-DEPENDENT phase 1 (EDP1)

  • Rate-limiting
  • Blocked by :
    1. divalent cations eg. Ca++ & Mg++
    2 hyperosmolarity (eg. Hyperosmolar Acidic urine)
    3 Decrease ph (hyperosmolar, acidic urine)
    4 Anaerobic Conditions
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22
Q

Impair Ability of bacteria to maintain membrane potential

A
  1. divalent cations eg. Ca++ & Mg++
    2 hyperosmolarity (eg. Hyperosmolar Acidic urine)
    3 Decrease ph (hyperosmolar, acidic urine)
    4 Anaerobic Conditions (Abscess)
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23
Q

bacterial cell wall

A

(porin channels )

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24
Q

periplasmic space

A

(passive diffusion)

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25
Q

cytoplasmic membrane

A

(active transport by proton pump-

an oxygen-dependent process)

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26
Q

linked to disruption of structure of cytoplasmic membrane disruption of cell envelope and other vital processes –
lethal action

A

energy-dependent phase II (EDP2)

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27
Q

primary IC site of action

A

30s ribosomal subunit

  • primary IC site of action
  • with 21 proteins and a single 16s molecule of RNA
  • 50s ribosomal subunit for others
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28
Q

Microbial Resistance

A

(1) Mutations in bacterial ribosome
(2) Acquisition of plasmids or transposon-encoding genes for aminoglycoside-metabolizing enzymes (AME) - inactivate AGS

(3) Impaired transport of drug into cell (cytosol)
- Transport : O2 –dependent active process
- Strictly Anaerobic bacteria- resistant
- Facultative bacteria grown in anaerobic conditions - resistant

(4) Efflux pumps - expel AGs from bact’l cells
(5) Low affinity of drug for the bacterial ribosome

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29
Q

exhibit similar activity vs most gram(-)

A

Tobramycin and Gentamicin

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30
Q

ABSORPTION

A

highly polar cations (highly charged)

  • DO NOT PERMIT THEIR MEMBRANE PERMEABILITY,
  • as a result they have very poor oral bioavailabilty entire oral dose excreted in faeces.
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31
Q

ABSORPTION: solubility

A

Polar! water soluble

do not penetrate most cells, CNS or eye (ex. Streptomycin)

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32
Q

Poorly absorbed where

A

GIT
< 1% absorbed after oral/rectal admin.
not inactivated in intestine & eliminated quantitatively in feces.

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33
Q

Long term administration

A

Renal impairment

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34
Q

absorption increased by GI dse. (ulcers/IBD)

A

Gentamicin

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35
Q

Rapid absorption?

A

1 absorption if instilled into body cavities with serosal surfaces

-toxic (ie. N-M blockade)

2 IM

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36
Q

Topical application for long a long time :

A

intoxication if with renal insufficiency

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37
Q

Peak conc. in plasma

A

30-90mins

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38
Q

Distribute poorly

A

Adipose Tse

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39
Q

Low concentrations in

A

secretions and tissues

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40
Q

High Conc in:

A

Renal cortex, endolymph & perilymph of inner ear

-Nephrotoxic & ototoxic

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41
Q

Increasing use of AGs via inhalation

A

Cystic fibrosis (w/chronic pseudomonas)

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42
Q

t/f
High sputum concentration
serum concentration remain LOW

A

True

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43
Q

For inhalation

A

tobramycin

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44
Q

Solutions for injections

A

Amikacin and tobramycin sol’ns

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45
Q

Active HEPATIC sec’n.

A

Conc in bile is 30% of those found in plasma (minor excretory route)

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46
Q

t/f Poor Penetration in respiratory sec’ns. or

47
Q

increase penetration in peritoneal and

pericardial cavities

A

Inflammation

48
Q

hearing loss in children

A

Streptomycin & tobramycin

49
Q

Distribution

A

In CSF- conc. (parenteral) – is subtherapeutic

Ocular fluid : penetration is poor

Pregnancy : accum. in fetal plasma & AF (NOT SAFE!!)

50
Q

Excretion almost entirely by

A

Glomerular filtration

Urine conc. – 50-200 ug/ml achieved

  • Nearly all of IV dose is excreted unchanged in urine.
  • Cleared by kidneys through glomerular filtration resulting in fairly high urinary conc. which makes them useful in UTI.
  • Use of urinary alkalinzer makes these drugs more effective.
51
Q

Single dose : disappearance from plasma exceeds renal excretion by %??

52
Q

: 100% of subsequent doses

- recovered in urine

A

After 1-2 days

53
Q

t/f

Rate of elimination is longer than plasma :

A

true

Tissue-bound aminoglycosides – 30-700 hrs.

10-20 days after : small amts seen in urine even after discontinuation

54
Q

Removed from body by : (overdose)

A

Hemodialysis & peritoneal dialysis

-50% removed in 12 hrs by hemodialysis

  • Peritoneal dialysis : less effective
    - Add antibiotic to dialysate if with bacterial peritonitis
55
Q

t/f

Can be inactivated by penicillin in vitro

A

true

In vivo with end-stage renal dse patients

Amikacin – least affected by this

56
Q

Half-lives prolonged in NB

A

8-11 hrs in 1st wk of life <2 kg

5 hrs > 2 kg

57
Q

Normal Half life

A

1.5 -3 hrs

58
Q

Clearance reduced in

A

Cystic Fibrosis

59
Q

Require Large doses

A

burn patients

- More rapid drug clearance 2ndary to drug loss thru burn tse.

60
Q

Dosing

A

Before : 2 Or 3 equally divided doses based on short t1/2

Higher doses once daily
- is as effective & less toxic
for patients with normal renal func.
provide longer period when concentration falls below threshold for toxicity

for G(+) - Not used if in combination with a cell wall-active agent eg. endocarditis
Can give multiple daily doses with lower total daily dose

If >2-3 days : monitor plasma to avoid drug accumulation

61
Q

Essential guide for proper admin. of drug

A

DETERMINATION OF CONC. OF DRUG IN PLASMA

In life-threatening systemic infxns. :
determined several times per week
w/in 24-48 hrs of a change in dosage

62
Q

Creatinine clearance

A

< 80-100 mL/min

Dose adjusted and plasma conc. monitored

63
Q

most accurate method of monitoring plasma levels for dose adjustment :

A

(1) Measure conc. in 2 plasma samples drawn several hrs. apart
- eg. at 2 and 12 hrs after a dose

(2) 
Nomograms 
Target ranges of :
- 1-1.5 ug/mL for gentamicin at 18 hrs for patients with creatinine clearance  >50 mL/min
- 1-2.5 ug/mL for <50 mL/min
Inaccurate

(3) Obtain a trough sample 24 hrs after dosing –
simplest method
but least desirable

64
Q

Ototoxicity

A
  • Dose-limiting adverse effect
  • Irreversible, bilateral high frequency hearing loss
  • temporary vestibular hypofunction
65
Q

produce predominantly VESTIBULAR effects

A

Streptomycin & Gentamicin

66
Q

Affect AUDITORY function

A

Amikacin, Kanamycin, Neomycin

67
Q

Affect VESTIBULAR AND AUDITORY

A

Tobramycin

68
Q

COCHLEAR TOXICITY (acute)

A

High pitched tinnitus
– often the first sx

Perception high-freq. sound lost first
– not aware of difficulty

69
Q

Symptomless in while in bed
Difficulty walking or make sudden movements
ATAXIA : most prominent feature

A

Chronic Labyrinthitis

70
Q

Chronic phase

A

persists for 2 months

71
Q

Recovery

A

require 12-18 mos.

Some with permanent residual damage

72
Q

Nephrotoxicity

A

8-26 % mild
and ALMOST ALWAYS REVERSIBLE
Proximal cells capacity to regenerate

-Initial mx of damage : excretion of nzs of renal tubular brush border

-after a several days:
Defect of renal concentrating ability
Mild proteinuria
Hyaline &amp; granular casts appearance
GFR : decreased after addn’l severaldays
non-oliguric phase : effect on distal portion of nephron
Mild Increase creatinine clearance
Infrequently : HYPO – K, Ca, PO4
73
Q

Nephrotoxicity accumulate in

A

Accumulation and retention in proximal tubular cells

74
Q

Decreasing potency for blockade

A

Neomycin, kanamycin, amikacin, gentamicin, tobramycin

75
Q

NEUROMUSCULAR BLOCKADE

A

Intrapleural & intraperitoneal instillation of large doses

Also with IV, IM oral

Most episodes : anesthesia with other N-M blocking agents

76
Q

Neuromascular Blockafe can be overcome by

A

Calcium can overcome this effect

Preferred tx : Ca salt (IV)

77
Q

Tx with ACHase inhibitors (NM blockage)

A

edrophonium & neostigmine

78
Q

Inhibit prejunctional release of Ach

A

NEUROMUSCULAR BLOCKADE :

79
Q

Uses

A

GRAM NEGATIVE INFECTIONS

DOC : lower cost & reliable activity vs all but the most resistant G(-) aerobes

Parenteral, opthalmic, topical

Gentamicin :
preferred agent but can be used interchangeably with :
Tobramycin, amikacin, netilmicin

80
Q

Preferred Agent

A

Gentamicin

81
Q

Used in combination with a cell wall-active agent (β-lactam or glycopeptide)

A

Rationale :
1 Expand spectrum of activity
For MDR G(-) : P. aeruginosa, Enterobacter, Klebsiella, Serratia

2 Provide synergistic bacterial killing
Improve microbial eradication & clinical response
in Endocarditis for G(+) eg. Enterococcus

3 Prevent emergence of resistance to individual agents
Only in Mycobacterial infections – data to prevent emergence
is supported by clinical data

82
Q

UTI/ Pneumonia

A

Gentamicin

Uncomplicated UTI :5mg/kg SD
Pyelonephritis : use w/B-lactam

Pneumonia : alone is ineffective;
-(best tx using B lactam, macrolides or flouroquinolones than aminogly

83
Q

used for asso. Cystic fibrosis

A

Gentamicin

84
Q

If betalactam is weak for sepsis add what

A

Gentamicin

85
Q

For burns

A

GENTAMICIN

Topical :
ointment- slow;
cream- more rapid;
> For burns

Meningitis : only for resistance to B-lactam (eg.Pseudo)

Peritonitis asso. w/ PD : 4-8 mg/L

Endocarditis : used w/ Penicillin

86
Q

Same with Gentamicin;
Superior activity for P. aeruginosa;
Used w/ B-lactams

A

TOBRAMYCIN

87
Q

Poor activity with Penicilin vs Enterococci (unlike gentamicin)

A

TOBRAMYCIN

88
Q

E.faecium - highly resistant;

Mycobacteria – ineffective;

A

TOBRAMYCIN

89
Q

LESS nephrotoxic and Ototoxic

A

TOBRAMYCIN

90
Q

IM/ IV /inhalation dose

Same dosages & serum conc. w/gentamcin;

Also Tobrex – an opthalmic ointment

A

TOBRAMYCIN

91
Q

Meningitis : only for resistance to B-lactam (eg.Pseudo)

A

GENTAMICIN

92
Q

Broadest spectrum of activity;
15 mg/kg/day
SD or div dose ( renal failure)

93
Q

Absorbed rapidly IM;

Peak plasma conc.: 20 ug/mL after 7.5 mg/kg injection;
30 min inf. IV : 40 ug/mL

94
Q

DOC for nosocomial G(-) infxns.

95
Q

Active vs M.tuberculosis & aypical mycobacteria (eg.in AIDS pt)

96
Q

Less effective vs Enterocci

than genta

97
Q

Renal/ Reversible

A

Gentamycin

98
Q

Vestibular/ Irreversible

A

Streptomycin

99
Q

Uncomplicated UTI : 1.5-2 mg/kg q 12h

Serious infxns.: 4-7 mg/kg SD or div dose

A

NETILMICIN

100
Q

For those resistant to genta; except Enterococci

A

NETILMICIN

101
Q

Broad antibacterial activity vs aerobic G(-) bacilli

A

NETILMICIN

102
Q

Latest drug;

Similar to genta & tobra;

A

NETILMICIN

103
Q

Bacterial Endocarditis :

w/penicillin (but genta is less toxic)

A

STREPTOMYCIN

104
Q

DOC (aside from Genta) :

for TULAREMIA

A

STREPTOMYCIN

105
Q

Plague

A

STREPTOMYCIN

106
Q

TB : 2nd line agent & always should be in combination w/1-2 drugs;
15 mg/kg/day IM x 2-3 mos.;

OPTIC nn dysfunc.,
scotomas,
periph.neurirtis

A

STREPTOMYCIN

107
Q

Rarely used because less effective than others

A

STREPTOMYCIN

108
Q

One of the most toxic;

Injection & oral use

109
Q

OBSOLETE

Can be used orally as adjuntive tx for hepatic enceph.

110
Q

Topical/ oral;

Topical : Alone or in combination with polymyxin, bacitracin, corticosteroids

111
Q

Skin & mucous mem. : burns, wounds, ulcers, infected dermatoses

112
Q

Oral : usually w/erythromycin: bowel prep.

For surgery; rarely for hep.enceph.;

w/ polymyxin B - bladder irrigation

113
Q 
Poorly absorbed in GIT; 
excreted by kidney like others;
6-8 % hypersensitivity rxns;
Renal damage;
nerve deafness

Pharmacology (4 decks)

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