Chloramphenicol Flashcards
What are the indications?
-Bacterial conjunctivitis
-otitis externa
-life-threatening infection where no other safer alternative can be used (allergy/ resistance) :
typhoid fever
h.influenzae
What is the spectrum of activity?
-broad spectrum
-against gram positive and gram negative
-aerobic
-anaerobic organisms
What is the mechanism of action?
Binds to ribosomes inhibiting protein synthesis
bacteriostatic
In high concentrations with highly susceptible organisms it can be bactericidal
What is the most common mechanism of resistance against chloramphenicol?
Production of acetyltransferase enzymes that directly inactivate the drug.
What are other mechanism of resistance?
-target modification
-decreased membrane permeability
-increased expression of efflux pumps
What are important side effects when used topically?
stinging
burning
itching
What are important side effects when used systemically?
-Significant risk of bone marrow toxicity
(with high dose use or drug accumulates due to impaired metabolism)
-Aplastic anaemia
-Grey baby syndrome -CIPCULAORTY COLLAPSE OCCURRING WHEN NEONATES EXPOSED AND UNABLE TO METABOLISE AND EXCRET DRUG
-Optic and peripheral neuritis (prolonged use)
Who should not be prescribed chloramphenicol?
allergy
personal or family history of bone marrow disorders
systemic-
third trimester of pregnancy
breast feeding
children<2 yrs (risk of grey baby syndrome)
dose adjustment and monitoring in hepatic impairment
(should be avoided topical in these groups of people)
What are important interactions
none when administered topically
how often should it be administered as eye drips and why?
If you’re using 0.5% chloramphenicol eyedrops,
put one drop into the affected eye every 2 hours (during waking hours) for the first 2 days.
Then every 4 hours for the next 3 days, or as your doctor advises.
regular use as blinking gets rid of drug
eye ointment can be used 3-4 times as a day so less likely to happen.
What are counselling points?
transient blurred vision may occur and that they should not drive until vision is clear.
Soft contact lenses may be damaged by eye drop preservatives and all contact lenses should be avoided during ocular infections.
eye drops/ointments are kept sterile.
wash hands before use
take care not to touch the tip,
discard any remaining drug at the end of the course.
If they purchase chloramphenicol over the counter for a self-diagnosed eye infection, they should seek medical advice if there is no improvement after 2days or if symptoms worsen, as this may indicate an incorrect diagnosis or superinfection with resistant organisms.
How long should treatment last for eye infections and why?
2days after healing avoiding prolonged topical treatment (>5-7 days) to limit toxicity
What are monitoring requirements for systemic use?
FBC- stopped if any signs of myelosupression
