Tuesday, October 6, 2009

Riley's antibiotic (chloramphenicol): Handle with care!

Chloramphenicol recrystallized and
photographed under the microscope
by The Molecular Expressions Collection
Kate, a BTB reader, asked about the antibiotic that Riley is getting. It's an interesting question with an equally interesting answer! The drug they prescribed at New Bolton is chloramphenicol. From what I'm hearing it's a pretty good choice for tough to fight infections. According to Veterinary Pharmacology and Therapeutics, it's "a broad-spectrum antibiotic, effective against gram negative and gram positive organisms, aerobic and anaerobic bacteria, and many intercellular organisms." It attains a high level of penetration into tissues, so it's prescribed a lot for treating areas of the body that are traditionally hard to treat -- the eye, central nervous system, the respiratory system, and hopefully bones.

So why isn't everyone using it?
There's a reason you don't see it used more widely -- there are some substantial risks for the humans administering it. If you don't handle it properly, the stuff can mess you up!
  • It can cause bone marrow suppresion (damage), which is thankfully reversible. This condition tends to occur at a certain level of exposure or dosage.
  • In rare cases it can cause irreversible aplastic anemia, with a fatality rate of 70%. A small percentage of people (estimated from 1 in 10,000 to 1 in 45, 000) are thought to be genetically susceptible. This condition is unrelated to dose or duration of exposure.
Because it is so toxic to humans, this drug should not be administered to animals who will be used as food or will produce food (e.g., milk).

The best practice for handling chloramphenicol is to never let it come into contact with your eyes, skin, mouth, or any body part. I had to sign a form that I had read and understood the risks before they gave me the prescription. Riley's formuation is basically a 25 gram paste tube that is administered two times a day. To administer this thick, fat tube of paste, you...
  • wear nitrile gloves (better protection than latex or rubber gloves)
  • wear a face mask
  • wear a long sleeved garment or apron that you can "peel off" if it gets paste on it
  • wipe any excess meds from walls, your horse's lips, and bedding. For permanent surfaces clean with soap and water.
  • Double bag any contaminated material, used tubes, etc. before throwing it away.

If any paste gets on your skin, you need to wash it off with soap and water and apply a layer of antibiotic ointment.

Riley got his first dose this morning -- in its natural form it's bitter, but apparently they sauce it up for palatability, and the barn manager told me he took it well. Riley's good about worming/tube paste, but this is a lot of paste, twice a day. I'll be suiting up!


Chloramphenicol Material Safety Data Sheet

Chloramphenicol in Veterinary Pharmacology and Therapeutics

Chloramphenicol in Equine Clinical Pharmacology

Chloramphenicol in Antimicrobial Therapy in Veterinary Medicine

Suit filed over the death of three thoroughbred horses from The Horse Magazine, October 18 2005

Chloramphenicol: The good, the bad, and the beware from Worms and Germs blog

Chloramphenicols from The Veterinary Formulary


  1. Daaaaamn. That is a big dog antibiotic. Never hear of it being given before.

    Is the Vet ordering regular CMP/CBCs while he is on this med to monitor for organ damage?

  2. It is not harmful to cats, dogs, horses - only people. The big problem with it, and other major antibiotics is developing a resistance.

    *I* should be monitored for organ damage :-). Fortunately Riley likes the taste and he dips his head so I can squirt it in.

  3. Thanks for the answer - that's very interesting - I've never encountered it and hope never to have the pleasure!

  4. That's acary stuff. I am sure you will extremely careful administering it.

    I even have trouble giving bute...i mix the powder in applesauce and use a dose syringe. But humans's taking bute is dangerous too as it causes a fatal anemia. I worry everytime I get some on me for fear I might ingest some.

    Not sure I would want to handle that antibiotic. But it surely does sound as if it will be a key component in Riley's recovery.

    Antibiotic resistance is a growing problem. They have been so over prescribed in humans that bacteria have mutated too quickly.

  5. Scary. That's good that he takes it well. I'd be nervous with my horse that he'd make a mess like he does with wormer.

  6. Interesting view under the microscope.

  7. That's scary! I guess this means you cannot kiss Riley on the lips for now...

  8. Oh, the things we do for our animals! Hope the healing continues to go well.

  9. That's some hardcore stuff! Holy cow. I'm just incoordinated enough that I'd have it everywhere. Hope it goes smoothly. So, did I read right: did you actually say human contact requires antibiotic cream to countereact the antibiotic? Interesting.


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