Rabbits

 

U.S. Ag Census data shows that rabbit production has increased in recent years. According to the 2012 Census of Agriculture (NASS), more than 5,000 farms sold almost 853,000 rabbits nationally. Rabbits are raised for meat, angora wool, breeding stock, pets and laboratory animals. Rabbits are considered a minor animal species by the U.S. FDA. As a result there are not many products labeled for use in rabbits.

Extra-label Drug Use

Since there are so few approved medications for use in rabbits, extra-label drug use is permitted according to the stipulations of AMDUCA.

Reminder: certain drugs are prohibited from use in food-producing animals, which includes rabbits!
  • Example: chloramphenicol is commonly used in clinical practice to treat pet rabbits, however, it is prohibited from use in food-producing animals.

Hind-Gut Fermenters

As hind-gut fermenters, the enteric bacterial flora naturally present in the cecum and intestines of the rabbits can be easily disrupted by antimicrobial medication administration, leading to a potentially fatal dysbiosis.

In general, orally administered antimicrobials are more likely to disrupt the intestinal microflora and cause diarrhea. The likelihood of developing clostridial overgrowth (Clostridial Enteritis and Enterotoxicosis in Rabbits) is especially increased if antimicrobials are given orally as opposed to administered parenterally. Rabbits are susceptible to this antimicrobial-induced colitis for as long as 10 days after stopping an antimicrobial regimen.

Narrower-spectrum antimicrobials tend to be more likely to cause antimicrobial-induced enterocolitis, such as: beta-lactams, macrolides and lincosamides. 

Below is a list of drugs that have been reported dangerous or fatal after use in rabbits:

Ampicillin: 40 to 100% fatal enteritis, dependent on dosage
Amoxicillin: Diarrhea after oral administration.
Cephalexin: Diarrhea after oral administration. Injection of cephalosporin has proven safe.
Clindamycin: Depending on dosage 50 to 100% fatal enteritis
Erythromycin: Diarrhea
Fipronil: Contraindicated for rabbits
Lincomycin: 33 to 100% fatal enteritis, dependent on dosage
Minocycline: Reduction of growth rate
Penicillin: Acute and/or chronic enteritis after oral administration.
Spectinomycin: Diarrhea
Spiramycin: Nervous signs
Tilmicosin: Fatal adverse reaction has been observed. The reaction seems rabbit dependent and it is advised to do a test dose of 5 mg/kg before doubling dosage.
Tylosin: Diarrhea
Vancomycin: Acute toxicity with 100% mortality

There is some evidence to show that a few antibiotics (Enrofloxacin (this use would be illegal ELDU if used in rabbit), Trimethoprim-Sulphonamide combinations) appear to be safe even when given orally for long periods.

Juveniles may be more susceptible to enterotoxaemia when on a high-starch diet than adults on a comparable diet. The risk of enterotoxaemia may be reduced by accurate dosing based on body weight, and administering antibiotics parenterally when possible. 
Rabbits on a balanced high-fiber diet with a healthy caecal microflora, may be less prone to disruption of the microflora following antibiotic use.

References:
Krempels, Dana. The Mystery of Rabbit Poop. http://www.bio.miami.edu/hare/poop.html

Merck Manual: Rabbit Nutrition

Morris, T. H. (1995). Antibiotic therapeutics in laboratory animals. Laboratory Animals, 29(1), 16-36.

Therapeutics in Rabbits

Toutain PL, Ferran A, Bousquet-Mélou A. Species differences in pharmacokinetics and pharmacodynamics. Handb Exp Pharmacol. 2010;(199):19-48. doi:10.1007/978-3-642-10324-7_2

Tulliez JE, Durand EF, Bories GF. Metabolic fate and pharmacokinetics of tissue residues of the anticoccidial drug robenidine in the rabbit. Incidence of coprophagy on its bioavailability. J Agric Food Chem. 1982;30(6):1071-1075. doi:10.1021/jf00114a016

Wheler, C.L. (2013). Antimicrobial Drug Use in Rabbits, Rodents, and Ferrets. In Antimicrobial Therapy in Veterinary Medicine (eds S. Giguère, J.F. Prescott and P.M. Dowling). doi:10.1002/9781118675014.ch36

Cecotropes

Rabbits produce two types of droppings: fecal pellets that are round and dry, and cecotropes that are nutrient-dense and consumed by the rabbit immediately upon excretion.

Unmetabolized drug residues excreted in the cecotrope may pose a risk because of recycling due to coprophagy. This can result in prolonged tissue drug residues, which can make a withdrawal interval determination difficult (Tulliez, 1982).

Medication Administration Considerations

  • Banana can be used to disguise the flavor of hard oral dosage forms, such as tablets and capsules
  • Caution should be used when administering topical medications, especially antimicrobial or steroid products. Due to their grooming habits, rabbits can experience systemic effects through consumption of topical preparations.