Pharmacology - Quinolones, Folic Acid Antagonists, Urinary Antiseptics, Metronidazole Flashcards
List the fluoroquinolones.
Ciprofloxacin, Levofloxacin, Moxifloxacin
What is the mechanism of action of the fluoroquinolones?
Targets DNA gyrase in Gram-negatives and topoisomerase IV in Gram-positives to inhibit DNA replication - inhibition of DNA replication results in bacterial lysis
How far should fluoroquinolones be spaced from consumption of dairy products or substances that contain divalent cations?
2h before or 6h after
How can fluoroquinolones be administered?
PO/IV/Opthalmic
What is the spectrum of action of ciprofloxacin?
Most active against Gram-negatives and enteric coliform (incl penicillin, cephalosporin and aminoglycoside resistant strains)
Highly effective against P.aeruginosa (only oral agent available)
Traveller’s diarrhoea caused by E.coli, food poisoning caused by all Enterobacteriaceae and Campylobacter jejuni
Typhoid fever caused by Salmonella typhi
Prostatitis
Anthrax caused by Bacillus anthracis
Uncomplicated UTI, but not recommended as first-line (mainly for penicillin allergy)
Avoid in MSSA/MRSA - is thus not considered a respiratory quinolone
What is the spectrum of action of levofloxacin?
Better Gram-positive coverage than ciprofloxacin - Streps and S.pneumoniae
(use for MSSA/MRSA coverage w caution)
Active against Gram-negatives - H.influenzae, E.coli, Klebsiella spp, Proteus mirabilis, Pseudomonas aeruginosa
Better coverage against Atypicals than ciprofloxacin
Useful against respiratory infections
NOT FIRST LINE FOR TB
What is the spectrum of action of moxifloxacin?
Better Gram-positive coverage than ciprofloxacin, esp S.pneumoniae, Finegoldia magna
(use for MSSA/MRSA coverage w caution)
Only used for H.influenzae amongst the gram negatives (no breakpoints from CLSI)
Better coverage against Atypicals than ciprofloxacin
Useful against respiratory infections
NOT FIRST LINE FOR TB
Are the fluoroquinolones used for CSF?
No
How are the fluoroquinolones excreted?
Renal - cipro, levo
Hepatic - moxi
All need adjustment in respective organ failures
Can fluoroquinolones be used in G6PD deficiency?
No
What are the adverse reactions associated with the fluoroquinolones?
- GI Sx - N/V/D
- Dysglycaemia risk, esp in DM
- Aortic dissections (rare)
- Inc C.diff colitis risk, esp w ciprofloxacin
- Headache and dizziness - treat CNS disorder pts carefully
- Phototoxicity
- Tendonitis risk
- QTc prolongation
- Peripheral neuropathy (can be reversible or irreversible)
What drugs interact w the fluoroquinolones?
The fluoroquinolones interact w warfarin and cyclosporine
What groups of patients are fluoroquinolones contraindicated in?
Children <18yo
Pregnancy
What is the mechanism of action of sulfamethoxazole?
Competitive inhibitors of dihydropteroate synthase, which stops dihydropteroic acid synthesis (immediate precursor of folic acid) - only active against microorganisms that solely synthesise their own folic acid
What is the mechanism of action of trimethoprim?
Inhibits reduction of dihyrofolic acid by dihydrofolate reductase to its active form, dec purine, pyrimidine & aa synthesis