Chloramphenicol

What is this medication for?

• Anaerobic infections (Clostridium, Bacteroides incl. fragilis); rickettsiae (RMSF); some gram-negatives (Salmonella, Brucella, Haemophilus); otitis; meningitis (CSF penetration); alternatives for multidrug-resistant organisms

How is it given?

Give exactly as your veterinarian prescribed — never change the dose or stop on your own unless your veterinarian has told you to.

• The 50S site is shared with macrolides/lincosamides — never combine (mutual antagonism).
• Human aplastic low red blood cell counts is the pharmacy-side concern: dispense with gloves warning, keep owners from direct contact with crushed tablets, and it's illegal in food animals.

What if I miss a dose?

• Give it as soon as you remember — unless it is almost time for the next dose (then skip the missed one; never double up).
• Call your clinic if you miss more than one dose in a row.

Side effects — what should I watch for?

Effects listed as common in this handout

• "Gray baby syndrome"-analog (Neonates/deficient conjugation)
• Anorexia, vomiting, diarrhea, depression (Common stomach/intestinal)
• Aplastic low red blood cell counts (HUMAN idiosyncratic risk (~1/24,000–40,000) — the reason for handler care and food-animal ban)

Worth a phone call to your veterinarian

• Reversible dose-related marrow suppression (myeloid/erythroid vacuolation, low infection-fighting cell counts, low platelet counts in cats) (Long-term therapy)

⚠️ Contact your veterinarian or an emergency clinic IMMEDIATELY if you notice

• Trouble breathing, collapse, seizures, severe vomiting or diarrhea, facial swelling, or pale gums

Before starting (or refilling), tell your veterinarian if your pet:

• has or has had: Food-producing animals — FDA-prohibited (extralabel AND label); neonates; breeding/pregnant animals
• has or has had: Hepatic failure (reduce dose); cats on prolonged high-dose (50 mg/kg every 12 hours × 2–3 wk = high adverse incidence — monitor closely)

• is pregnant, nursing, or used for breeding
• is taking any other medications, supplements, or flea/tick products, including:
  • Phenytoin, phenobarbital
  • Warfarin
  • Erythromycin/clindamycin/tylosin (50S competitors)
  • Bactericidal antibiotics (beta-lactams, aminoglycosides)
  • Digoxin

Storage and handling

Room temperature. Human handler warning: gloves for administering; never handle if personally exposed to aplastic-low red blood cell counts risk.

Good to know

• CSF/eye/prostate penetration is chloramphenicol's superpower — historically the drug for CNS infections when culture supports it.
• The 50S site is shared with macrolides/lincosamides — never combine (mutual antagonism).
• Human aplastic low red blood cell counts is the pharmacy-side concern: dispense with gloves warning, keep owners from direct contact with crushed tablets, and it's illegal in food animals.
• Cats: every 12 hours not every 8 hours, watch thrombocyte counts; dogs tolerate every 8 hours at 40–60 mg/kg.