Analgesia Guidelines

Find recommended analgesics by species, as well as general information about analgesia for rodents. 

Analgesia relieves pain without loss of consciousness. 

Pain is difficult to assess in animals, so indirect signs are often used to identify pain, including abnormal posturing, vocalization, decreased appetite, and self-mutilation.  

Because of the difficulty in determining when an animal is in pain, animal welfare regulations require providing analgesia whenever a procedure is being performed or a condition is present that is likely to cause pain. In the absence of evidence to the contrary, it is assumed that something that is painful in humans will also be painful in animals. 

Analgesia is best provided pre-emptively, or prior to the painful procedure, rather than after observing clinical signs of pain. Systemic and/or local analgesics may also reduce anesthetic requirements. Several viable options exist to relieve pain in laboratory animals.

Opioids: Buprenorphine, fentanyl

Opioids exert their effects on the opiate receptors in the central nervous system. Opioids are effective for acute, deep, or visceral pain. 

The most commonly used opioid in laboratory animal medicine is buprenorphine, which manages mild to moderate pain. Potential side effects include respiratory depression, nausea, vomiting, pica (rats), and constipation. Sustained-release buprenorphine has been associated with dermatitis and ulceration at the site of administration in rats and mice. 

All opiates are controlled substances, and their use requires special record keeping.

Non-steroidal anti-inflammatory drugs (NSAIDs): Carprofen, meloxicam, ketoprofen

Generally, the NSAID classification applies to drugs that inhibit one or more steps in the metabolism of arachidonic acid (AA). NSAIDs act primarily to reduce the biosynthesis of prostaglandins by inhibiting cyclooxygenase (COX). 

NSAIDs are effective for pain associated with inflammation. On their own, NSAIDs are effective against pain of mild to moderate intensity.

Potential side effects include gastric or intestinal ulceration, disturbance of platelet function, and changes in renal function.

Local analgesia: Lidocaine, bupivacaine

Local analgesics may be administered by several techniques. Anesthetic effects are seen within 15 minutes of administration and may last from 45 minutes to several hours, depending on the drug used.

• Infiltration or infusion: Injection beneath the skin and other tissue layers along the site of an incision before or after a procedure.
• Field block, ring block: Injection into soft tissues distant from the actual incision in a pattern that intersects the nerve supplying the surgical site.
• Nerve conduction block: Infusion of a small amount of drug or directly adjacent to the sheath of a nerve supplying the surgical site.
• Topical local anesthetics, such as lidocaine jelly, may be useful for some surgical wounds.

Note that the doses provided do not apply for epidural administration.

Rodents: General information about analgesia