protein synthesis inhibitors Flashcards
what is the target of rifampin ?
RNA polymerase
which part of the protein synthewsis stage do these antibiotics work ?
in the translation phase
what are the aminoglycosides ?
gentamicin , tobramycin, streptomycin
what is the mechanism of aminoglycosides ?
block the initiation of protein synthesis
primarily bind to 30S
what is the problem or draw back with using amino glycosides ?
they cannot be used against anaerobes
not effective in intracellular organisms
most protein synthesis inhibitors are bacterio ?
bacteriostatic except aminoglycosides are bacteriocidal
what drugs are given prior to bowel surgery ?
neomycin with erythromycin
what drug has a synergistic effect with aminoglycosides ?
beta lactamase inhibitors
what drugs are used for Cystic fibrosis patients ?
piperacillin and tazobactam along with tobramycin
because the targeted organism is usually pseudomonas
what drug combo can be used for newborn meningitis ?
vancomycin gentamycin
what is the most common mechanism of resistance with aminoglycosides ?
aminoglycosides modifying enzymes
by adding acetyl groups or by phosphorlyation
what are the toxicities of ahminoglycosides ?
1- ototoxicity and balance problems whe tKEN NWIITH LOOP DIIUURETICS
2- nephrotoxicity ( ATN)
3- neuromuscular blockade ( usually with pre existing neuromuscular disease )
4- teratogenic
what are the methods of monitoring levels of aminoglycosides ?
plasma levels : trough and peak levels
high trough - risk of toxicity
low peak - less effective therapy
what are the macrolides ?
azithromycin
clarithromycin
erythromycin
what is the mechanism of macrolides ?
bind to the 50 s ribosomal sub unit
specifically bind to the P site which is the exit tunnel
hence blocking the process of translocation
what are the three sited associated with ribosomes ?
A - new tRNA brings in an amino acid
P - growing peptide chain is held at the P site
E - used tRNA exit here
what antibiotic is commonly associayed with the blocking of the enzyme peptide transferase ?
chloramphenicol
why are macrolides considered effective against intracellular pathogens ?
because they are concentrated inside macrophages
good drug to cover for pneumonia ?
macrolides
what are the common infections in which macrolide can be used ?
community acquired pneumonia
chlamydia infections
what is the mechanism of erythromycin ?
binds to motilin receptors in the GI tract
stimulates smooth muscle contraction
used for motility disorders
what is clarithromycin commonly used for ?
part of triple therapy of h pylori
what antibiotic is used for IBS ?
erythromycin
what are the methods of mechanism agaisnt macrolides ?
23 rRNa altering , the location where the macrolide bind
the bacteria will phophorylate this are to avoid macrolides binding to it
what are the adverse effects of macrolides ?
1- nausea diarrhea and abdominal pain
2- prolonged QT on ekg ( potassium blocking)
3- acute cholestatic hepatitis
what are the contraindications associated with macrolide use ?
patients who already have QT prolongation
patients with pre existing liver disease
patients with a history of macrolide allergy
myasthenia gravis
what drugs inhibit P450 enzyme, and what is the consequent effect ?
clarithromycin and erythromycin
means that drugs that are normally metabolized by p450 stay longer in the body
what are the main drugs that are metabolized by P450 ?
theophylline and warfarin
what are the tetracyclines ?
tetracycline
doxycycline
demeclocycline
what is the mechanism of tetracyclines ?
binds to 30S ribosome
prevents attachement of tRNA
what is demeclocycline used for ?
not used as an antibiotic
used as an ADH antagonist
instead used to treat SIADH
causes nephrogenic DI to reverse to SIADH
what are the clinical scenarios are associated with doxycycline ?
used for acne vulgaris
used with intracellular pathogens
zootonic
community acquired MRSA
what impairs the absorption of tetracyclines?
minerals and antacids:
calcium magnesium \iron \dairy
what are the mechanisms of resistance against tetracyclines ?
decreasing influx or increasing efflux
what are the adverse effect of tetracyclines ?
GI distress
photosensitivity
dicoloration of the teeth ( children under the age of 8 )
inhibition of bone growth
teratogenic
what is the mechanism og chloramphenicol ?
inhibits peptidyl transferase at 50S ribosomoal unit
what are the clinical uses of chloramphenicol ?
meningitis
rickettsial disease
what are the dangers of using chloramphenicol in pregnant patients ?
if used in the third trimester can cause gray baby syndrome
what are the main side effects of chloramphenicol ?
anemia
aplastic anemia
gray baby syndrome
what is the mechanism of clindamycin ?
binds to 50s ribosomal subunit
binds to 23S rRNA component
prevents translocation
what is the mechanism of resistance of clindamycin?
same as macrolides
methylation of the binding site of the macrolide
which is the 23s rRNA
what are the clinical scenarios associated with clindamycin ?
anaerobic infections above the diaphragm such as lung abscess , aspiration pneumonia
what is the main adverse effect of clindamycin ?
pseudomembranous colitis
c difficile
which bacteria is associated with a high resistance to clindamycin ?
B fragilis
what is the mechanism of linezolid ?
binds to the 50 S ribosome
blocks the initiation of protein synthesis
what is the main clinical use of linezold ?
VRE
what is the clinical scenario associated with patients who have VRE ?
usually a hospitalized patient with prior antibiotic treatment
what are the adverse effects of linezolid ?
because it is a weak MAO inhibitor it can cause seretonin syndrome
especially when co administered with an SSRI
what drugs are used for vancomycin resistant bacteria ?
synercid
what are the common organusms associated with pneumonia in cystic fibrosis patients ?
Pseudomonas aeruginosa, Staphylococcus aureus, and Burkholderia cepacia.
