Ketamine-Xylazine Combination for Rodent Anesthesia

The combination of ketamine and xylazine is popular for the anesthesia of many species including rodents. Ketamine is a dissociative anesthetic and Xylazine is a powerful sedative/analgesic. The effective dose may vary with strain, sex, and age of the animal.

Dosage ranges that have been used:

Mice: Ketamine 80-200 mg/kg and Xylazine 7-20 mg/kg
Rats: Ketamine 80-100 mg/kg and Xylazine 5-10 mg/kg

Suggested starting doses are:

Mice: Ketamine 100 mg/kg and Xylazine 10 mg/kg
Rats: Ketamine 80 mg/kg and Xylazine 8 mg/kg

Combining drugs:

The drugs may be combined together and administered as a single intraperitoneal (IP) injection.

Example:

The following regimen will produce a surgical level of anesthesia lasting 15-30 minutes and sedation of 1-2 hours.

Combine: 1ml Ketamine (conc. 100mg/ml)
0.5ml Xylazine (conc. 20mg/ml)
8.5ml Normal saline 0.9% or PBS
Dosage: For mice: 0.1ml per 10 gm of body weight
For rats: 0.08 ml per 10 gm body weight
Route: Intraperitoneal injection using 1 ml syringe 23-25 gauge 5/8 inch needle

Other notes:

- Fasting rodents is not necessary and is not recommended.
- Repeating administration for lengthening anesthesia is risky. Xylazine is longer acting that Ketamine and it is critical to not overdose with Xylazine. One-half the original dose may be tried or repeat only the Ketamine. Supplementation with Isoflurane gas anesthesia works well if additional anesthesia is needed.
- Ketamine and Xylazine should be diluted with saline or PBS as above for mice and small rats to ensure accurate measurement of volumes used.
- Mixtures of ketamine and xylazine are not stable and may lose potency in a weeks time after mixing. Date of mixing should be placed on container or bottle used.
- The animals should be kept dry, insulated, or warmed to prevent excessive loss of body heat. Ophthalmic ointment should be applied to the eyes to prevent drying of the corneas seen as opaqueness.
- Ketamine and Xylazine can be purchased through the Veterinary Pharmacy Bldg 14, ORS Division of Veterinary Resources. Ketamine is a class III controlled substance.