Analgesics-Rat
The detection of pain perception in individual rodents is based on subjective evaluation of behavioral
and attitudinal changes as well as on objective analysis of physiologic parameters. Behavioral signs
indicative of pain perception include reluctance to move, abnormal posturing, decreased appetite,
vocalization, anxiety, apprehension, hypersensitivity, depression, aggression and polyphagia of bedding.
In addition to behavioral changes physiological signs of pain perception include fluctuation in blood
pressure, heart rate, respiratory rate, body temperature, and food and water consumption resulting in
changes in body weight. Their behavioral, attitudinal, and physiological signs of pain perception are
currently the best methods available to detect individual rodents that are in some degree of pain as well
as to assess the success/failure of ongoing analgesic therapy.
For analgesic treatment in rats nonsterodial anti-inflammatory drugs (NSAIDs) and opioids are most
commonly used. While NSAIDs such as acetaminophen, aspirin, carprofen, diclofenac, flunixin,
ibuprofen, paracetamol and piroxicam are primarily indicated for the treatment of low to moderate
intensity inflammatory pain, opioids are used to combat moderate to severe pain.
Analgesics may be administered to rats either parenterally or orally. Oral formulas are available for
morphine, butorphanol, oxycodone, codeine, and meperidine. However, when adding drugs to drinking
water the risks include inaccurate dosing, lack of consumption due to palatability, and degradation of
the agent over time due to hydrolysis.
This information is intended to aid investigators in designing an analgesic protocol for a group of rats.
Drug name
Acetaminophen
Acetylsalicylic acid
Buprenorphine
Buprenorphine
Buprenorphine
Butorphanol
Carprofen
Codeine
Diclofenac
Flunixin meglumine
Ibuprofen
ketoprofen
Ketorolac
Ketorolac
meloxicam
meperidine
meperidine syrup
Dose (mg/kg)
1-2 mg/mL
100-150 mg/kg
0.01-0.05 mg/kg
0.1-0.25 mg/kg
0.02 mg/mL
1-2 mg/kg
5 mg/kg
25-60 mg/kg
10 mg/kg
2.5 mg/kg
10-30 mg/kg
5 mg/kg
3-5 mg/kg
1 mg/kg
1 mg/kg
20 mg/kg
0.2 mg/mL
Route of administration
Drinking water
PO
SC, IV
PO
Drinking water
SC
PO, SC
SC
PO
SC
PO
PO, SC
PO
SC, IM
PO, SC
SC, IM
Drinking water
Morphine
Nalbuphine
Oxymorphone
Pentazocine
Piroxicam
2-5 mg/kg
4-8 mg/kg
0.2-0.5 mg/kg
10 mg/kg
3 mg/kg
SC
IM
SC, IM
SC
PO