antibiotic 2 Flashcards
what are some examples of aminogylcosides
gentamicin
amikacin
MOA for gentamicin
bind irreversibly to bacterial ribosomes (30s subunit) - inhibit protein synthesis
bactericidal
enter bacterial cells via O2 dependent transport system (strep and anaerobic does not have this system, so resistance)
what are organisms are gentamicin good for
spectrum incl - gram -ve aerobic bacteria, staphylococci and mycobacteria - it depends on O2 dependent mechanism to enter the bacteria cells
strep and anaerobic bacteria does not have this mechanism so resistant
what does gentamicin resistance come into existence
reduced cell membrane permeability to aminoglycoside
acquire enzyme which modify aminoglycoside to prevent them reaching to ribosome
indication for gentamicin
severe sepsis - incl unknown source
pyelonephritis and complicated UTI
biliary and other intra-abdo sepsis
endocarditis
contra-indication for gentamicin
aminoglycosides are excreted in renal
can cause renal, cochlear and vestibular damages especially in elderly and neonates
renal impairment
can impair neuromuscular transmission so should not be given to myasthenia gravis
side effect of gentamicin
nephrotoxicity
ototoxicity - tinnitus, vertigo
interaction of gentamicin
ototoxicity - with loop diuretics or vancomycin
nephrotoxicity - with ciclosporin (immunosuprresant), platinum chemo, cephalosporins or vancomycin
what are some examples of macrolides
clarithromycin
erythromycin
azithromycin
-mycin
MOA for erythromycin
binds to 50s subunit of ribosome
which one of the macrolides have the greatest anti-bacterial activity?
erythromycin -come from a bacteria and hence nature - has great G+ve but little G-ve affects
Clarithromycin and Azithromycin - are synthetic and so have greater G-ve activity
contra-indication for clarithromycin
macrolide hypersensitivity
excepted in the liver - hepatic impairment
dose reduction in renal impairment
side effect of clarithromycin
most common and severe with erthromycin
macrolides are irritants - N+V, abdo pain, and diarrhoea
allergy, antibiotic-associated collitis
cholestatic jaundice
prolongation of QT interval
ototoxicity at high dose
indication for clarithromycin
respiratory infection
skin and soft tissue infection - alternative for penicillin
severe pneumonia - added to penicillin
eradication of H.pylori (along with metronidazole or amoxicillin)
interaction of erythromycin
erythromycin and clarithromycins are p450 cytochrome inhibitors
- warfarin - inc risk of bleeding
- statins - inc risk of myopathy
QT intervals prolong drugs - - amiodarone, antipsychotics, quinine, quinolone antibiotics, SSRIs
what are the examples of quinolones
ciprofloxacin
moxifloxacin
levofloxacin
- floxacin
MOA of ciprofloxacin
inhibiting DNA synthesis
what are the ability of quinolones
active aginst G-ve organisms - UTI and GI tract infection
moxifloxacin and levofloxacin - newer and active against G+ve - RTI as well
indication of quinolones
- UTI
- severe GI tract infection
- lower RTI - moxifloxacin and levofloxacin
- ciprofloxacin - only antibiotics which can be used against pseudomonas aeruginosa
contra-indication for quinolones
caution in those who might have seizures
those who are growing - potential arthropathy
QT prolongation - cardiac disease or electrolyte disturbance
side effect of quinolones
GI upset - N+D
immediate and delayed hypersensitivity
neurological effects - lowering seizure threshold
rupture of muscle tendons
prolong QT interval - increase risk of arrhythmia
C.diff colitis
interaction of quinolones
drugs containning divalent cations eg Ca+, antacidds, reduce absorption and efficacy of quinolones
ciprofloxacin - P450 cyctochrome inhibitors - theophylline
Co-prescription with NSADs - inc seziures with prednisolone - inc risk of tendon rupture
drugs which prolongs the QT intervals - amiodarones, antipsychotics, quinine, macrolide, SSRIs
what are some examples of glycopeptide
vancomycin
MOA of vancomycin
inhibits growth and cross-linking of peptidoglycan chains
inhibit synthesis of cell wall of G+ve only and inactive against most G-ve
indication for vancomycin
G+ve infection - endocarditis (esp in the case of MRSA)
antibiotic associateed colitis - C.Diff (usually 2nd line where metronidazole is ineffective)
contra-indication for vancomycin
close monitoring for toxicity
renal impairment
elderly - inc risk of hearing impairment
side effect of vancomycin
pain and thrombophlebitis (vein inflammation)
if infused too quickly - - red man syndrome - erythema and hypoTN and bronchospasm
allergy
nephrotoxic
ototoxicity
blood disorder - neutropenia and thrombocytopenia
interactions of vancomycin
ototoxicity and nephrotoxicity when with amioglycoside, loop diuretics or ciclosporin (immunosuppresants)
what drug class is metronidazole
anaerobic antibiotics
MOA of metronidazole
reduction of metronidazole in anaerobic bacteria - cause DNA degradation and cell death
only anaerobic bacteria can reduce metronidazole so aerobic bacteria is not effective
indication for metronidazole
antibiotic associated colitis - C.Diff
Oral infection or aspiration pneumonia - G-ve anaerobes from mouth
surgical and gynaecological infection - G-ve anaerobes from the colon
protozoal infection - trichomonal vaginal infection, amoebic dysentery, giardiasis (parasitic infection)
contra-indication for metronidazole
metabolised by cyctochrome P450
liver impairment
alcohol should not be drunk during the course of metronidazole - metraonidazole inhibit the enzyme required for alcohol metabolism
side effect of metronidazole
GI upset - N+V
hypersensitivtiy reaction
neurological - peripheral and optic neuropathy, seizures and encephalopathy - if prolonged used
interaction of metronidazole
some inhibitory effect on cytochrome P450 - warfarin and phenytoin
cytochrome P450 inducers eg rifampicin and phenytoin - result in inc plasma conc
inc risk of toxicity with lithium
