Antibiotics Flashcards
Concentration dependent
do not underdose
Aminoglycosides eg. gentamicin
Quinolones eg. moxifloxacin
Time dependent
do not skip doses
Beta lactams
BETA LACTAMS-where do they act?
Cell wall
are beta lactams time dependent or concentration dependent?
Bacteriocidal or bacteriostatic
time dependent
bacteriocidal
adverse side effect beta lactams
hypersensitivity
beta-lactams resistance
Cannot be overcome by using higher doses – In community most aerobic Gram negatives, anaerobes & staphylococci produce β-lactamases
– Extended spectrum β-lactamases in aerobic Gram negatives in hospitals,
which results in high level resistance to all penicillins & cephalosporins
beta-lactams second resistance
mutations in penicillin binding proteins
(e.g. S. pneumoniae) – usually low level resistance, which can be
overcome by using higher doses
Macrolide chief example
Azithromycin
macrolide mechanism of killing
no protein synthesis 50s ribosome
what do macrolides treat
Gram pos
Strep/staph infections that can’t be treated by penicillin
Atypical pneumonia causes: legionella, mycoplasma, chlamydophila
Macrolide toxicity
GIT symptoms
H pylori DOC
azithromycin
M avium complex in AIDS DOC
azithromycin
– Chlamydia urethritis/cervicitis DOC
azithromycin single
Tetracycline main drug
doxycycline-absorption varies, penetrates cells easily
Limited use for resp infections as strep pneu is often resistant
Tetracycline MOA
inhibits 30 S ribosome synthesis
bacteriostatic
resistance tetracycline
enzymatic breakdown
toxicity tetracycline
nausea/vomiting, photosensitivity, teeth discolouration (avoid <8 years/pregnancy)
DOC
Rickettsia
– Brucellosis
– Acne (low dose)
TETRACYCLINES
PROPHYLAXIS FALCIPARUM MALARIA
tetracyclines
Chlamydia STI (urethritis, PID)
2 antibiotics to treat
tetracyclines (superseded by azithromycin)
Sulphonamide plus trimethoprim
cotrimoxazole
Cotrimoxazole MOA
– Block successive steps in bacterial folate pathway
– Prevents nucleic acid synthesis
cotrimoxazole side effects
Main side effect is sulphonamide hypersensitivity
– Skin rashes – may be severe (Stevens-Johnson
Syndrome/Toxic Epidermal Necrolysis) or +/- systemic
cotrimoxazole resistance
mainly used in HIV otherwise
toxicity & high
prevalence of resistance in community-acquired
Gram negatives and S. pneumoniae
HIV Pneumocystis jirovecii pneumonia
– Toxoplasmosis
– Cystoisospora belli diarrhoea
treatment
Cotrimoxazole
HIV primary prophylaxis
cotrimoxazole
Prevents above & reduces bacterial infections
Toxic to DNA (forms highly reactive nitro
radical with anaerobic metabolism Fe:S proteins)
Metronidazole
short course metronidazole
metallic taste
Disulfiram-like effect (avoid alcohol)
long course metronidazole side effects
neutropaenia
neurotoxic
what does metronidazole treat
a lot!
It is a broad-spectrum anaerobe agent:
Cocci,
Gram- bacilli,
Gram+ spore-forming bacilli
Also effective protozoans lacking mitochondria:
– Entamoeba histolytica
– Trichomonas vaginalis
– Giardia lamblia (ETG)
What does penicillin 1 act against
Gram + and spiros DOC: Streptococci (few S. pneumoniae highly resistant) – Syphilis & other spirochaetes – Enterococci – Listeria (gram positive bacillus) – Actinomyces
Aminopenicillins:
and how they are different from regular penicillin?
Amoxicillin
Treats: gram +, spiros and haemophilus
GOOD FOR RESP TRACT INFECS-STREP PNEU
diff. from reg. penicillin because cover h. influ (gram neg)
Which penicillin resists Beta-lactamase from Staphylococci?
Cloxacillin
which penicillin is better absorbed orally
flucloxacillin
cloxacillin and flucloxacillin
Both only for Gram positive bacteria
Widely used for skin and soft tissue infections
Amoxicillin-clavulanate
broad spectrum
community-acquired Gram positive, Gram negative &
anaerobe infections
1st gen cephalosporin and what does it treat
Cefazolin IV
Streptococci and staphylococci
3rd gen cephalosporin and what does it treat
ceftriaxone
streptococci staphylococci Gram - (CA) Haemophilus Typhoid Spirochaetes CNS good pene
ceftriaxone what does it treat?
Good CSF penetration & empiric drug of choice for
bacterial meningitis
– Drug of choice for typhoid
– Drug of choice for gonorrhea (IMI)
– Useful broad spectrum agent for serious community
infections
Excreted mainly bile
– Spectrum community-acquired Gram+ (including most S. pneumoniae,
not ideal for S. aureus)
& Gram-
Glycopeptide antibiotic
Vancomycin
time dependent
not oral
what does vancomycin treat
ONLY GRAM POS-Especially cloxacillin-resistant Staphylococci
Vancomycin toxicity
IV
Slow IV infusion essential (red man syndrome)
– Mildly nephro- /oto-toxic
– Measure concentration in renal failure & selected
organisms
Aminoglycosides don’t like
AEROBIC GNB
aminoglycoside MOA
inhibit protein synthesis
polar-poor tissue penetration
aminoglycosides
parenteral
conc dependent killing
aminoglycoside example
gentamicin
gentamicin
Pyelonephritis
– Combined with β-lactams for polymicrobial
infections or synergy (enterococci, streptococcal
endocarditis)
aminoglycoside toxicity
prolonged elevated trough conc
ototoxicity
nephrotoxicity
quinolones MOA
Targets DNA enzymes (gyrase & topoisomerase IV)
CONC DEPENDENT
2nd gen quinolone
ciprofloxacin doc: Drug of choice – Bacterial dysentery – Pyelonephritis & prostatitis • Alternative to aminoglycosides • Typhoid (resistance is increasing)
Gram- aerobes (including Pseudomonas) – poor for Gram+
3rd gen quinolone
Moxifloxacin
Gram+ (esp Streptococci) and Gram- (except Pseudomonas)
MDR TB
• Alternative for respiratory tract infections (only if severe beta lactam
allergy), cover atypical pneumonia agents as well as conventional
bacterial causes of community-acquired pneumonia
toxicity quinolones
rashes
CNS
tendonitis
