Chloramphenicol

Chloramphenicol is a broad-spectrum phenicol antibacterial used for selected infections in companion animals and non-food-producing horses. It distributes widely into tissues and cells and has activity against many susceptible aerobic and anaerobic organisms. Its veterinary applications include infections where resistance patterns, tissue penetration or the need for anaerobic coverage favor its use.

Group

Amphenicol antibacterial

Mechanism of Action

Chloramphenicol binds the 50S bacterial ribosomal subunit at the peptidyl-transferase region. This inhibits formation of peptide bonds during protein synthesis, preventing production of proteins needed for bacterial growth and function. Its action is usually bacteriostatic, although some highly susceptible organisms may be killed at achievable concentrations. Broad tissue distribution supports activity at intracellular and other less accessible infection sites.

Dose Rates

Dogs

Use / stage	Dose	Route	Schedule	Instructions
Bacterial infections	40–50 mg/kg	PO	Every 8 h
Injectable sodium succinate treatment	Reference only	IV		Chloramphenicol sodium succinate 40–50 mg/kg IV or IM every 6–8 hours; different prodrug formulation and dose basis.
Bacterial infections	45–60 mg/kg	PO	Every 8 h	Up to 14 days; Oral course 7–14 days in university antimicrobial guidance; monitor CBC and clinical response.
Urinary, rickettsial or localized soft-tissue infection	25–50 mg/kg	PO	Every 8 h	Up to 7 days
Systemic infection	50 mg/kg	PO	Every 6–8 h	Up to 5 days; Oral alternative, course 3–5 days.
Rocky Mountain spotted fever	15–20 mg/kg	PO	Every 8 h	Up to 21 days; Historical alternative, course 14–21 days.
Infectious otitis	50 mg/kg	PO	Every 8 h
Parenteral infection alternatives	Reference only	IV		Sodium succinate injectable alternatives include 45–60 mg/kg IM/SC/IV every 6–8 hours; 50 mg/kg every 6–8 hours for systemic infection for 3–5 days; or 50 mg/kg every 4–6 hours for severe bacteremia for up to three days. Require a compatible injectable product and active-equivalent strength.

Cats

Use / stage	Dose	Route	Schedule	Instructions
Bacterial infections	12.5–20 mg/kg	PO	Every 12 h
Bacterial infections	50 mg/animal	PO	Every 12 h	Alternative fixed oral dose.
Injectable sodium succinate treatment	Reference only	IV		The earlier per-cat injectable line conflicts with weight-based regimens. The supplement and university antimicrobial guidance independently support 12–30 mg/kg IV every 12 hours; that is added separately, retaining this discrepant record for review.
Bacterial infections	25–50 mg/kg	PO	Every 12 h	Historical higher oral alternative; marrow toxicity is a particular feline concern.
Urinary or localized soft-tissue infection	50 mg/animal	PO	Every 12 h	Up to 14 days
Severe bacteremia or sepsis	50 mg/animal	PO	Every 6–8 h	Up to 5 days; Historical oral fixed-dose alternative; reassess marrow risk and use a suitable route for severity.
Bacterial infections	12–30 mg/kg	IV	Every 12 h	Chloramphenicol sodium succinate, strength expressed as chloramphenicol equivalent. Distinct from the inconsistent earlier per-cat injectable line.
Other parenteral infection alternatives	Reference only	IV		Historical sodium succinate alternatives include 12–30 mg/kg IM/SC/IV every 12 hours; 50 mg per cat every eight hours; or 25–50 mg/kg every 12 hours for systemic infection, generally no more than 14 days. High feline marrow risk requires close reassessment.

Horses

Use / stage	Dose	Route	Schedule	Instructions
Highly susceptible bacterial infections	35–50 mg/kg	PO	Every 6–8 h	Oral absorption is low and variable; restrict interpretation to highly susceptible organisms.
Bacterial infections	45–60 mg/kg	PO	Every 8 h
Foal bacterial infection	20 mg/kg	PO	Every 4 h	Foals only; oral form. A separate IV regimen needs an appropriate sodium succinate preparation.
Foal sodium succinate treatment	Reference only	IV		Foals: chloramphenicol sodium succinate 25–50 mg/kg IV every 4–8 hours; oral chloramphenicol base/palmitate alternative is 40–50 mg/kg every 6–8 hours.

Rabbits

Use / stage	Dose	Route	Schedule	Instructions
Bacterial infections	30–50 mg/kg	PO	Every 8–24 h	Oral regimen; parenteral alternatives require sodium succinate preparation.

Hedgehogs

Use / stage	Dose	Route	Schedule	Instructions
Bacterial infections	50 mg/kg	PO	Every 12 h

Chinchillas

Use / stage	Dose	Route	Schedule	Instructions
Bacterial infections	30–50 mg/kg	PO	Every 12 h

Guinea pigs

Use / stage	Dose	Route	Schedule	Instructions
Pneumonia	30–50 mg/kg	PO	Every 12 h
Injectable sodium succinate treatment	Reference only	SC		20–50 mg/kg of the succinate salt SC every 6–12 hours; salt-mass regimen must not be converted using a base-equivalent preparation without an explicit basis.

Gerbils

Use / stage	Dose	Route	Schedule	Instructions
Injectable sodium succinate treatment	Reference only	SC		20–50 mg/kg of the succinate salt SC every 6–12 hours; salt-mass regimen must not be converted using a base-equivalent preparation without an explicit basis.

Hamsters

Use / stage	Dose	Route	Schedule	Instructions
Injectable sodium succinate treatment	Reference only	SC		20–50 mg/kg of the succinate salt SC every 6–12 hours; salt-mass regimen must not be converted using a base-equivalent preparation without an explicit basis.

Mice

Use / stage	Dose	Route	Schedule	Instructions
Injectable sodium succinate treatment	Reference only	SC		20–50 mg/kg of the succinate salt SC every 6–12 hours; salt-mass regimen must not be converted using a base-equivalent preparation without an explicit basis.

Rats

Use / stage	Dose	Route	Schedule	Instructions
Injectable sodium succinate treatment	Reference only	SC		20–50 mg/kg of the succinate salt SC every 6–12 hours; salt-mass regimen must not be converted using a base-equivalent preparation without an explicit basis.

Ferrets

Use / stage	Dose	Route	Schedule	Instructions
Proliferative colitis	50 mg/kg	PO	Every 12 h	Up to 21 days; Course 14–21 days.

Birds

Use / stage	Dose	Route	Schedule	Instructions
Bird sodium succinate treatment	Reference only	IM		Sodium succinate alternatives: 80 mg/kg IM two to three times daily; 50 mg/kg IV three to four times daily; or 50 mg/kg IM/IV every eight hours. Preserve salt basis and use a verified injectable preparation.
Bird oral palmitate treatment	Reference only	PO		Palmitate 30 mg/mL suspension: 0.1 mL per 30 g three to four times daily, or 75 mg/kg orally every eight hours. Absorption is erratic; do not use for initial life-threatening infection or with crop stasis.

Reptiles

Use / stage	Dose	Route	Schedule	Instructions
Reptile sodium succinate treatment	Reference only	IM		Sodium succinate 20–50 mg/kg IM/SC for up to three weeks lacks a repeat interval; another alternative gives 30–50 mg/kg per day IV/IM for 7–14 days. Maintain exact salt basis.

Indications

Treatment of susceptible bacterial skin, wound and soft-tissue infections in dogs and cats, including selected multidrug-resistant staphylococcal infections.
Treatment of selected susceptible respiratory, systemic or central nervous system infections in companion animals when tissue penetration supports its use.
Treatment of susceptible anaerobic or mixed aerobic–anaerobic infections in companion animals.
Treatment of selected infections in non-food-producing horses caused by highly susceptible organisms; clinical success is influenced by variable oral exposure.

Contraindications

Do not use in food-producing animals.
Avoid pregnancy and neonatal use.
Avoid prolonged treatment in cats.
Preexisting nonregenerative anemia or other hematologic abnormality requires extreme caution.
Severe hepatic dysfunction or renal impairment may cause accumulation; neonatal kittens are especially vulnerable.

Interactions

Inhibits metabolism of several anesthetics, opioids, barbiturates, phenytoin and salicylates through CYP inhibition.
Cimetidine can increase chloramphenicol exposure; rifampin can reduce it.
Other myelosuppressive agents increase marrow risk, and chloramphenicol may delay response to iron, folate or vitamin B12.
Lidocaine, propofol and barbiturate effects may be prolonged, particularly in cats.

Adverse effects

Gastrointestinal upset
Reversible marrow suppression, especially in cats
Reversible peripheral neuropathy and weakness in dogs

Toxicity

Human exposure can cause rare irreversible aplastic anemia. Animals can develop dose-related marrow suppression; discontinue for significant cytopenia or neuropathy.

Preparations

Preparation	Form	Strength	Route
Chloramphenicol 100 mg tablet	Tablet	100 mg / tablet	PO
Chloramphenicol 250 mg tablet	Tablet	250 mg / tablet	PO
Chloramphenicol 500 mg tablet	Tablet	500 mg / tablet	PO
Chloramphenicol 250 mg capsule	Capsule	250 mg / capsule	PO
Chloramphenicol palmitate oral suspension 30 mg/mL Palmitate prodrug; active-equivalent basis is not specified and is not assumed.	Oral Liquid	30 mg / mL	PO

Monitoring and Administration

Monitor CBC with prolonged therapy, especially beyond 14 days in cats. Prevent accidental exposure during handling, including exposure to children.

Equine oral absorption is variable; activity at typical regimens is unreliable unless the organism is highly susceptible, approximately MIC ≤2 mcg/mL.

Palmitate oral formulations depend on enzymatic conversion and should not be given to fasted or anorectic animals. Injectable sodium succinate is a different prodrug; do not substitute its mass automatically for oral chloramphenicol.

Aqueous chloramphenicol preparations are described as stable for 24 hours. Sodium succinate stability is formulation-specific; a 30-day room-temperature or six-month frozen period is described.

Discard cloudy sodium succinate solution. Prevent exposure during crushing or compounding; chloramphenicol is not appropriate in food-producing animals.