The following list includes only the commonly used anesthetic agents in rats. A list of other anesthetics suitable for specific procedures and additional information about the effects, mode of action, metabolism, and side effects of these agents are available in the CMU office, extension 6555.  The use of an anticholinergic (atropine, 0.04 mg/kg, intramuscularly, subcutaneously, or intraperitoneally) may help reduce salivation and maintain heart rate.

INJECTABLE AGENTS:

Note:  The doses of injectable anesthetic agents can vary depending upon the genetic background of the rat.  In some rats, the therapeutic dose is very close to the lethal dose.  The doses provided here are intended as a guide, and they may have to be adjusted for different strains or stocks of rats.

Ketamine - 44-100 mg/kg by intramuscular injection. COMMENTS: Lower dose produces sedation, higher dose range produces light surgical anesthesia, poor muscle relaxation, incomplete analgesia, not suitable for procedures requiring moderate to deep anesthesia, lasts about 30 minutes or less, time to recovery is longer.

Ketamine + acetylpromazine - 75 mg/kg ketamine + 2.5 mg/kg acetylpromazine by intramuscular injection (can be mixed together in the same syringe). COMMENTS: More muscle relaxation than #1, incomplete analgesia, not suitable for procedures requiring moderate to deep anesthesia, lasts about 30 minutes or less, time to recovery is longer.

Ketamine + xylazine - 40-87 mg/kg ketamine + 5-13 mg/kg xylazine by intramuscular or intraperitoneal injection. COMMENTS: Good analgesia and muscle relaxation, suitable for more invasive procedures than Ketamine or Ketamine and Acetylpromazine and those of short to medium duration, causes hypothermia and hypotension, can be reversed at least partially with 1.0-2.1 mg/kg yohimbine by intraperitoneal injection.

Ketamine + xylazine + acetylpromazine - Mix 1.5 ml of ketamine (100 mg/ml) with 1.5 ml of xylazine (20 mg/ml) and 0.5 ml of acetylpromazine (10 mg/ml), give 0.5 - 0.7 ml/kg by intramuscular or subcutaneous injection.  Intraperitoneal injection MAY also be suitable. COMMENTS: Suitable for most surgical procedures, good muscle relaxation and analgesia.

Pentobarbital - 30-40 mg/kg by intravenous injection; 30-60 mg/kg by intraperitoneal injection. COMMENTS: Some variation in effect in rats depending on genetic background; poor analgesia; suitable for mildly invasive procedures at higher dose range; can last 20-30 minutes.

INHALANT AGENTS:

Carbon dioxide - Administer in an enclosed container such as a bell jar using bottled CO2, given to effect, optimal concentration is 70% CO2 + 30% O2.  COMMENTS: Generally safe so long as not overdosed, suitable only for very brief procedures  - 1-2 minutes or less.

Halothane – Halothane should be administered with a vaporizer.  Anesthesia can be induced with 3 – 5% Halothane and maintained at 1.0 – 1.5% of inspired gas.  COMMENTS:  Rapid induction and changes in levels of anesthesia make Halothane dangerous when used without a vaporizer; waste gases should be scavenged for personal safety reasons; microsomal enzymes are induced to a greater degree than with methoxyflurane; suitable for prolonged procedures when administered with a vaporizer; rapid recovery.

Isoflurane - Administer with a vaporizer. Anesthesia can be induced with 3 – 5% isoflurane and maintained at 1 – 2% of inspired gas.  Rats may be intubated (using a 14 - 18 gauge over the needle catheter; please see the CMU staff for specific guidance and instruction) or anesthetized with a face mask. COMMENTS:  Rapid induction and changes in levels of anesthesia make isoflurane dangerous when used without a vaporizer, waste gases should be scavenged for personal safety reasons; the anesthetic concentration of isoflurane required to anesthetize hypertensive strains (e.g., SHR and Wistar-Kyoto) is significantly lower than that for normotensive rats; suitable for prolonged procedures when administered with a vaporizer; rapid recovery; can be cardioprotective in some species.