Guidelines on Anesthesia and Analgesia in Rats

Unit for Laboratory Animal Medicine
Oct 15, 2013 12:00 am

This document has been designed by the ULAM veterinary staff as a guideline for sedation, anesthesia, and analgesia of laboratory rats. This is not intended to be an inclusive tutorial on all possible drug combinations that can be used in rats. The following guidelines are also general recommendations and consequently do not include reference to specific research associated concerns.

All surgical procedures, anesthetics, analgesics, antibiotics or other medications used on animals must be approved by the IACUC, described in the animal use protocol and performed by personnel listed on the protocol and appropriately trained for the surgical procedure. Any techniques or drug protocols deviating from this document must be justified and approved in the IACUC protocol prior to application.

  • Responsibility

    1. Principal Investigator: Responsible to ensure appropriate anesthesia and/or analgesia is provided for all rodents undergoing painful procedures including rodent survival surgery unless otherwise indicated in the relevant approved protocol.
  • Glossary Definitions


    Central depression causing stupor where the animal is unaware of its surroundings but still responsive to painful procedures.

  • Procedures

    1. Prior to Anesthetic/Analgesic/Sedative Event

    1. Newly arrived animals should be acclimated at least 3 days prior to anesthesia or sedation.
    2. Age and body weight should be considered when designing an A/A plan.
    3. Preanesthetic fasting is usually not necessary in rodents. If preanesthetic fasting is required:
      1. The fasting period must be limited to 2-3 hours and no longer due to the higher metabolism in rats.
      2. Water should NEVER be restricted.
    4. Ocular lubrication such as Paralube® must be used to prevent corneal drying during anesthesia or sedation.

    2. Routes of Administration

    1. More detailed information regarding injection techniques and maximum quantities safely administered to rats can be found in Guidelines on Administration of Substances to Laboratory Animals.

    3. Normal Monitoring Parameters

    1. More information on anesthetic/sedation monitoring requirements can found in Anesthesia and Sedation Monitoring Guidelines.
      1. Respiratory rate should be 70 - 110 breaths/min.
        1. A drop in respiratory rate of 50% can be normal during anesthesia.
        2. Respiratory pattern can be used to monitor anesthesia.
          1. Deep and slow or rapid and shallow.
      2. Pulse rate should be 260 - 500 beats/min.
      3. Normal temperature ranges while under anesthesia fall between 35.9°C and 37.5°C (96.6 - 99.5°F).
      4. Mucus membrane color should be pink. Never pale white or blue.
        1. Normal capillary refill time (CRT) is < 2 seconds.

    4. Recovery

    1. More information on monitoring parameters during post-operative recovery can be found in Guidelines on the Performance of Surgery in Rodents.
    2. Recover animals in clean cages without bedding to limit possibility of tracheal foreign body obstruction or pneumonia.
    3. Recover animals in the surgery area so they can be appropriately monitored during the recovery period.
    4. Animals that have received an alpha-2 agonist (xylazine, dexmedetomidine) as part of their anesthetic protocol may receive a reversal agent to expedite recovery (see Table 3).
    5. If a large number of surgeries are being conducted at one time, animals may be housed together following anesthesia and prior to full recovery if they are continually observed. This is to ensure that more alert animals do not cannibalize non-responsive cage mates.
    6. Nutritional support is critical following anesthesia and should be provided as soon as the animal is recovered.
      1. Moist chow, regular chow, or diet gel should be provided on the cage floor to encourage eating as soon as possible.

    5. Anesthetics

    1. Detailed information on all approved anesthetics and sedatives can be found in Anesthesia and Analgesia Drug Descriptions.
    2. Anticholinergics
      1. Atropine 0.05 mg/kg subcutaneously
      2. Glycopyrrolate 0.01 - 0.02 mg/kg subcutaneously 
    3. Table 1: Inhalant Anesthetics Used in Rats


         Dosage and Route   



         4 - 5% for induction   
         1 -2% for maintenance   

         Requires use of calibrated vaporizer   


         Ambient vaporization of   
         ether-soaked gauze   

         Use in fume hood due to its flammable and explosive nature.   
         Notification of EHS required.   

    1. Table 2: Injectable Anesthetics and Tranquilizers Used in Rats


         Dosage and Route a   







         40 - 50 mg/kg IP   
         80 - 95 minutes   
      • Poor analgesic effects. Dose sufficient to produce surgical anesthesia may cause severe respiratory depression and death.
      • Avoid buprenorphine co-administration.  Buprenorphine and pentobarbital will result in cardiorespiratory depression. Administer buprenorphine after full recovery.





         + Xylazine   
         40 - 90 mg/kg ket. IP   
         + 5 - 10 mg/kg xyl. IP   
         45 - 90 minutes   
      • Thermal support is crucial. To prolong anesthesia, supplement with 1/3 dose of ketamine only. Xylazine can be reversed with 1 - 2 mg/kg yohimbine IP or 0.1 - 1.0 mg/kg atipamezole IP/SQ 
         + Acetypromazine   
         75 - 80 mg/kg ket. IM or IP   
         + 2.5 mg/kg ace. IM or IP   
         20 - 30 minutes   
      • Light anesthesia
         + Dexmedetomidine   
         75 mg/kg ket.   
         + 0.25 - 0.5 mg/kg. dex. IP   
         for non-premedicated animals.   
         75mg/kg ket.   
         + 0.03 - 0.1 mg/kg dex. IP   
         for animals premedicated with   
         buprenorphine or other opioids.   
         120 minutes   
      • Light anesthesia   
      • Reverse dexmedetomidine with atipamazole 1.0 mg/kg IP      
         + Diazepam   
         40 - 80 mg/kg ket. IP   
         + 5 - 10 mg/kg dia. IP   
         20 - 30 minutes   


         + Xylazine   
         + Acepromazine   
         31.25 mg/kg ket. IP or IM   
         + 6.25 mg/kg xyl. IP or IM   
         + 1.25 mg/kg ace. IP or IM   
      • (Welberg et al. 2006)   

         Neuromuscular Blocking   
         Agents (NMBA)   




         2 mg/kg IV





         a- Chloralose   
         (5% w/v concentration)   
         Not Recommended   
         31 - 65 mg/kg IP   
      • Poor analgesia, possible convulsions, metabolic acidosis. Do NOT use for survival surgical procedures.   
         a- Chloralose   
         + Urethane   
         Not Recommended   
         50 - 60 mg/kg chl. IP   
         + 500 - 800 mg/kg ure. IP   
         (administer urethane 20-30 min.   
         prior to a- chloralose)   
         500 minutes   
      • Do NOT use for survival surgical procedures. Can be used for prolonged non-recovery monitoring procedures.   
         Chloral hydrate   
         (5% concentration)   
         Not Recommended   
         300 - 450 mg/kg IP   
         60 - 136 minutes   
      • Concentration above 5% produces peritonitis. Anesthetic dose is near the lethal dose. Do NOT use for surgical procedures. Can be used for sedation for monitoring procedures.   
         (ethyl carbamate)   
         (50% w/v concentration)   
         Not Recommended   
         1000 - 1500 mg/kg IP   
         Up to 24 hours   
      • Carcinogenic and mutagenic DO NOT use for survival surgical procedures.   
      • For non-recovery use only due to progressive acidosis, hyperosmolality of body fluids, and osmotic toxicity to mesenteric vasculature.   
       a Subcutaneous (SC), Intramuscular (IM), Intraperitoneal (IP), Intravenous (IV)
    1. Table 3: Injectable Reversal Agents Used in Rats


         Dosage and Route a   


         Atipamezole (Antisedan)   

         0.1 - 1.0 mg/kg IP, IM or SC   

         Preferred reversal agent for alpha-2 agonists   


         1.0 - 2.0 mg/kg IP or SC   

         Less effective than atipamezole   

       a Subcutaneous (SC), Intramuscular (IM), Intraperitoneal (IP), Intravenous (IV)

    6. Analgesics

    1. Signs of Pain in rats may include, but are not limited to, the following:
      1. Reluctance to move
      2. Decreased activity
      3. Unresponsive
      4. Abnormal posturing
      5. Back arching
      6. Decreased appetite
      7. Ungroomed hair coat
      8. Vocalization
      9. Piloerection
      10. Self-mutilation
      11. Social isolation
    2. Prevention and Management of Pain
      1. For short-term management (less than seven days) of moderate to severe pain, the ULAM veterinary staff recommends subcutaneous injections of buprenorphine (0.01 - 0.05 mg/kg) two to three times per day. A single injection of buprenorphine will typically last eight hours, but there is considerable variation in duration. The animals should be observed carefully so that the optimum dose and frequency of administration can be determined. 
    3. Table 4: Analgesics Used in Rats


         Dosage and Route a   


         Buprenorphine (Buprenex®) b   

         0.01 - 0.05 mg/kg SQ, IP   

         8 - 12 hours   

         Carprofen (Rimadyl®)   

         5 mg/kg SQ   

         24 hours   

         Flunixin (Banamine®)   

         2.5 mg/kg SQ   

         12 - 24 hours   

         Ketoprofen c   

         5 mg/kg SQ   

         24 hours   

         Meloxicam (Metacam®)   

         1 - 2 mg/kg SQ or PO   

         24 hours   

       a Subcutaneous (SQ), Intramuscular (IM), Intraperitoneal (IP), Intravenous (IV), Orally (PO)
       b Preemptive analgesia, particularly opiates like buprenorphine, can reduce the dose of anesthetics required for surgical anesthesia and increase the respiratory depression associated with anesthetics. When preemptive analgesia is used, consider reducing the dose of anesthetic (whether inhalant or injectable) to the low end of the recommended range. Anesthetic depth must be carefully monitored and drug doses may need to be titrated to maintain appropriate levels. With new projects, sexes, strains or anesthetic analgesic combinations, assess a subset of animals before expanding to use in a larger cohort.
       c Current literature (Shientag 2012) and institutional reports have identified a potential ketoprofen sensitivity in some rat stocks and strains. Therapeutic doses of ketoprofen (5mg/kg), under the right physiologic conditions, may cause gastrointestinal bleeding, erosion, ulceration, and, in extreme cases, perforation. Rats receiving ketoprofen for analgesia should be closely monitored for signs of gastrointestinal complications within 24-48 hours after administration.

    7. Local Anesthetics

    1. Maximum safe doses for most species including rats are:
      1. Lidocaine: 4 mg/kg (0.4 ml/kg of a 1% solution)
      2. Bupivacaine: 1-2 mg/kg (0.4-0.8 ml/kg of a 0.25% solution)

    8. Neonatal Rodent Anesthesia

    1. A rodent neonate is a mouse or rat <10 days of age. There are several anesthetic methods in the literature for use in neonatal rodents however, hypothermia is the primary physical method utilized in neonatal rodent anesthesia. It is believed to provide anesthesia and temporary analgesia by decreasing neural conduction and synaptic transmission. The cooling process may be painful and direct contact with the cooling agent should be avoided.
      1. Injectable anesthetics have been associated with a high mortality in neonatal rodents.
      2. Neonatal rodents may have a longer induction and recovery time than adult rodents with inhalant anesthetics.
    2. Hypothermia - Can only be performed in neonatal rodents <6 days old and should not be used for procedures lasting longer than 30 min.
      1. Place neonates either on a latex covered bed of crushed ice, in a cut off finger of a latex glove, or in a paper-lined test tube in crushed ice.
      2. Check the pup for pedal reflex indicating proper plane of anesthesia.
      3. Remove the pup from the ice bed and place on a chilled cold pack or bed of ice. Place a barrier between the pup and the ice to prevent direct damage to the tissues.
      4. Use fiber optic lighting for the surgical field as incandescent bulbs may warm the pup.
      5. Following hypothermia anesthesia, re-warm the animals slowly. Rapid warming can cause tissue damage. Use of a circulating water heating pad (40 ºC) or in an incubator (33 ºC) is recommended.
      6. Return pups to dam once they are able to crawl.
    3. Parental cannibalism can occur with neonates after anesthesia. The following steps can be used to reduce the occurrence of cannibalism in anesthetized neonatal pups:
      1. Ensure the neonate is fully recovered before returning to the dam.
      2. Smear the pups with soiled bedding from the mother's cage.
      3. Place the pup back in the middle of the litter.
  • References

    1. Arras M, Autenried P, Rettich A, Spaeni D, Rulicke T. 2001. Optimization of intraperitoneal injection anesthesia in mice: drugs, dosages, adverse effects, and anesthesia depth. Comp Med 51:443-456.
    2. Baumans V, Coke C, Green J, Moreau E, Peterson-Kane E, Reinhardt A, Reinhardt V, Van Loo P eds. Making Lives Easier for Animals in Research Labs, Animal Welfare Institute, Washington, DC, 2007.
    3. Clowry, Gavin (2000).The successful use of fentanyl/fluanisone (Hypnorm) as an anesthetic for intracranial surgery in neonatal rats. Laboratory Animals34, 260-264.
    4. Danneman, Peggy (1997).Evaluation of Five Agents/Methods for Anesthesia of Neonatal Rats. Laboratory Animal Sciences47, 386-395.
    5. Dobromylskyj P, Flecknell PA, Lascelles BD, Pascoe PJ, Taylor P, Waterman-Pearson A. 2000. Postoperative and acute pain. In: Flecknell PA, Waterman-Pearson A, editors. Pain management in animals. London: W.B. Saunders. p 81-145.
    6. Flecknell, P. Laboratory Animal Anesthesia, 2nd Edition. Academic Press, 1992.
    7. Flecknell P, Waterman-Pearson eds. Pain Management in Animals, WB Saunders. London England, 2000.
    8. Fox JG, Anderson LC, Loew FM, Quimby FW eds. Laboratory Animal Medicine 2nd Ed. Academic Press, London England, 2002.
    9. Gaynor J, Muir W, Handbook of Veterinary Pain Management, Mosby, St. Louis Missouri, 2002.
    10. Gotoh, Hideo (2004).General Anesthesia of infant mice by isoflurante inhalation for medium-duration surgery. Experimental Animal53, 63-65.
    11. Hawk CT, Leary SL, Morris TH editors. Formulary for Laboratory Animals, 3rd Edition, Blackwell Publishing, Ames, Iowa, 2005.
    12. Hrapkiewicz K, Medina L, Holmes D, Clinical Laboratory Animal Medicine 2nd ed. Iowa Sate University Press, Ames, Iowa, 1998.
    13. Lieggi CC, Fortman JD, Kleps RA, Sethi V, Anderson JA, Brown CE, Artwohl JE, "An evaluation of preparation methods and storage conditions of tribromoethanol" Contemporary Topics in Laboratory Animal Science. 44.1 (2005) Pg 11-16.
    14. Meyer RE, Fish RE. "A review of tribromoethanol anesthesia for the production of genetically engineered rats and mice." Lab Animal. 34.10 (2005).
    15. National Institutes of Health, Office of Animal Care and Use: "Pain and Distress in Mice, Rats, and Rabbits: Responsibilities, Recognition and Alleviation" updated 7/2004.
    16. Ness RD. 2005. Rodents. In: Carpenter JW, editor. Exotic animal formulary. St. Louis: Elsevier Saunders. p 386-393.
    17. Phifer, C.B. (1986).Use of Hypothermia for General Anesthesia in Preweanling Rodents. Physiology and Behavior38, 887-890.
    18. Shientag, LJ, et al. 2012. A therapeutic dose of ketoprofen causes acute gastrointestinal bleeding, erosions, and ulcers in rats. JAALAS 51(6):832-841.
    19. Sharp, P, Villano, J, The Laboratory Rat 2nd ed. CRC Press, Boca Raton, Florida, 2013.
    20. Wixon, SK and Smiler, KL. Anesthesia and Analgesia in Rodents, Chapter Nine. In: Anesthesia and Analgesia in Laboratory Animals. DJ Kohn, SK Wixon, WJ White, GJ Benson, Eds., Academic Press, 1997.
    21. Wright-Williams SL, Courade JP, Richardson CA, Roughan JV, Flecknell PA. 2007. Effects of vasectomy surgery and meloxicam treatment on faecal corticosterone levels and behavior in two strains of laboratory mouse. Pain. 130(1-2): 108-18.
    22. Zeller W, Meier G, Burki K, Panoussis B. "Adverse effects of tribromoethanol as used in the production of transgenic mice." Laboratory Animal Science. 32.4 (1998) Pg 407-413.
    23. Other websites describing guidelines for Avertin use:
    24. Other Websites regarding neonatal rodent anesthesia:
Species: Rats

If you have questions or comments about this document, contact ULAM Veterinary Staff ( or 734-936-1696).

The ULAM Training Core ( or 734-763-8039) can be contacted to provide training in techniques at no charge.

For any concerns regarding animal health after work hours or on holidays/weekends, contact DPS (3-1131) who will contact the on-call veterinarian.