Antibiotics Flashcards
What is the mechanism of trimethoprim?
Interferes with DNA synthesis by inhibiting dihydrofolate reductase
What are the adverse effects of trimethoprim?
Myelosuppression
Transient rise in creatinine: trimethoprim competitively inhibits the tubular secretion of creatinine resulting in a temporary increase which reverses upon stopping the drug
Why does trimethoprim increase creatinine?
locks the ENaC channel in the distal nephron, causing a hyperkalaemic distal RTA (type 4).
It also inhibits creatinine secretion, often leading to an increase in creatinine by around 40 points (but not necessarily causing AKI)
What is the mechanism of doxycycline?
Bacterialstatic
- Protein synthesis inhibitor
- binds to 30S subunit blocking binding of aminoacyl-tRNA
What is the resistant mechanism of doxycycline?
increased efflux of the bacteria by plasmid-encoded transport pumps, ribosomal protection
What is the choice of antibiotic for UTI in pregnant women?
- Nitrofuantoin (avoid in close to term)
- Amoxicillin or cefalexin
What antibiotic must be avoided in methotrexate?
Trimethoprim
Co-trimoxazole
What is the mechanism of action of rifampicin?
Inhibits RNA synthesis
Bacteriostatic
What antibiotics are bacterial static?
Bacteriostatic antibiotics
chloramphenicol
macrolides
tetracyclines
sulphonamides
trimethoprim
What antibiotics are bactericidal?
Bactericidal antibiotics
penicillins
cephalosporins
aminoglycosides
nitrofurantoin
metronidazole
quinolones
rifampicin
isoniazid
What antibiotics stop cell wall synthesis?
penicillins: binds transpeptidase blocking cross-linking of peptidoglycan cell walls
cephalosporins
What antibiotics inhibit protein synthesis?
aminoglycosides (cause misreading of mRNA)
chloramphenicol
macrolides (e.g. erythromycin)
tetracyclines
fusidic acid
What antibiotics stop DNA synthesis?
quinolones (e.g. ciprofloxacin)
metronidazole
sulphonamides
trimethoprim
What antibiotics stop RNA synthesis?
Rifampicin
What is red man syndrome and what causes it?
Vancomycin
Ototoxicity, nephrotoxicity and red man syndrome. Red man syndrome is associated with flushing or a maculopapular rash. The proposed mechanism is non IgE mediated mast cell degranulation. Red man syndrome is more common with higher flow rates of infusion. Treatment includes antihistamines.
What is the coverage of linezolid?
Spectrum, highly active against Gram positive organisms including:
MRSA (Methicillin-resistant Staphylococcus aureus)
VRE (Vancomycin-resistant enterococcus)
GISA (Glycopeptide Intermediate Staphylococcus aureus)
Adverse effects of linezolid?
Adverse effects
thrombocytopenia (reversible on stopping)
monoamine oxidase inhibitor: avoid tyramine containing foods
Mechanism of action of linezolid?
Linezolid is a type of oxazolidinone antibiotic which has been introduced in recent years. It inhibits bacterial protein synthesis by stopping the formation of the 50s initiation complex and is bacteriostatic in nature.
