Fluoroquinolones (Abx) Flashcards
What is the general action of fluoroquinolones?
Bactericidal
Directly inhibit bacterial DNA synthesis which prevents replication and ultimately causes cell death
Name some common fluoroquinolones
Ciprofloxacin
Ofloxacin
Levofloxacin
Moxifloxacin
Delafloxacin
Norfloxacin
What are the oral bioavailability of the different fluoroquinolones?
Ciprofloxacin = 70%
Moxifloxacin = 86%
Ofloxacin = > 95%
Delafloxacin = 70%
Norfloxacin = 30-40%
Which of the common fluoroquinolones is only available as an oral formulation?
Norfloxacin
Describe the pharmacokinetics of ciprofloxacin
Oral bioavailability = 50-85%
Protein binding =
Half-life = 3-5 hours
Metabolism = hepatic (inhibits CYP1A2)
Excretion for oral administration = 30-50% kidneys, 15% metabolised, 30% presystemic clearance (hepatobilliary and faecal)
Excretion for IV administration = 70% kidneys, 10% metabolised
Describe the pharmacokinetics of levofloxacin
Oral bioavailability = 99%
Protein binding =
Half-life = 6-8 hours
Metabolism = Does not undergo CYP450 metabolism + does not inhibit/induce CYP450 enzymes
Excretion (for oral/IV administration) = 87% kidneys, < 1% metabolised, < 4% faeces
Describe the pharmacokinetics of ofloxacin
Oral bioavailability = > 90%
Protein binding =
Half-life = 5-7.5 hours (prolonged in renal impairment)
Metabolism = Does not undergo CYP450 metabolism + does not inhibit/induce CYP450 enzymes
Excretion (oral/IV administration) = 80% kidneys, 4% metabolised, 4-8% faeces
Which substances should be avoided when taking fluoroquinolones?
Antacids
Mineral supplements
Certain oral medications
Can reduce the bioavailability by 90% in some cases
Are fluoroquinolones broad or narrow spectrum?
Broad
Potent activity against aerobic, enteric gram-negative bacilli and many common respiratory pathogens
A 80-year-old diabetic male patient presents with very painful venous ulcers on his left gaiter area. O/E the ulcers were weepy, with a greenish film over them. Which organism is responsible for the superimposed infection and what Tx will you give him?
Pseudomonas
Ciprofloxacin (1st line)
Which disease can fluoroquinolones make an individual at higher risk of getting?
C. difficile-associated disease
What is the typical dosing of ciprofloxacin?
500-750mg PO BD
400mg IV 8-12 hours (given over 60 minutes)
Eye drops QDS
What is the typical dosing of levofloxacin?
500mg PO/IV OD/BD
What is the typical dosing of ofloxacin?
200-400mg PO/IV BD
What are the indications for ciprofloxacin?
Superficial bacterial eye infection (inc. severe)
Corneal ulcer
Acute otitis externa
Moderate/severe diabetic foot infection
Fistulating Crohn’s disease
Acute diverticulitis (used in combo with metronidazole)
Respiratory tract infections
Pseudomonal lower respiratory tract infection in CF
UTIs
Acute prostatitis
Uncomplicated gonorrhoea/disseminated gonococcal infection
Surgical prophylaxis
Anthrax (Tx + pre-exposure prophylaxis)
Prevention of secondary case of meningococcal meningitis
Acute pyelonephritis, UTI (catheter related)
