Used to reduce pain are initiated pre-emptively during the surgical period and continued well into the postoperative recovery period. It is often erroneously presumed that an animal is not in pain, when there is no obvious change in behavior. Pain can be difficult to detect because of individual and species variation. "Typical" signs of pain include guarding the painful area, vocalization, licking, biting, self mutilation, signs of depression, grinding of teeth, restlessness, lack of mobility, failure to groom, abnormal posture, changes in sleep patterns, and failure to eat or drink. Pain can be assumed to have been present if administration of analgesics causes these signs to disappear.
Consultation with the attending veterinarian is recommended since there is tremendous variation between species as to their response to analgesic drugs. Limited animal studies have been conducted and for many species there will be widely different published dosage schedules. Never extrapolate from human data, please consult with the veterinarian.
Guidelines for the administration of analgesics
- Medical and veterinary reports suggest analgesics are most effective when administered prior to the painful stimulus, before the surgical incision and tissue manipulation.
- Analgesic drugs must be given at the proper initial dose and subsequent doses must be given according to schedule.
- Federal law requires pain relief according to the same guidelines for a human patient undergoing a similar procedure.
In addition to the care which must be taken when choosing the proper dosage and schedule for a particular species, different analgesics are indicated for different types of pain:
- Nonsteroidal anti-inflammatory agents (NSAID) are effective against pain associated with inflammation, acute pain associated with soft tissue injury, burns, and pain associated with bone injuries or disease. However, severe pain in any of these categories may be best treated with NSAID's in combination with potent opioid agonists. Examples include: banamine, ibuprofen.
- Opioid agonists are effective against most visceral and somatic pain; although generally not as effective as NSAID's against bone pain, they may be used in conjunction with NSAIDs to treat severe bone pain. Examples include: morphine, meperidine.
- Opioid agonist-antagonists are effective against mild to moderate visceral and somatic pain. Examples include: buprenorphine, butorphanol.
- Neurogenic pain is pain which arises from damaged nerves or from amputation. This pain is difficult to treat and rarely responds well to any of the drugs listed above. More likely to be effective: tricyclic antidepressants such as amitriptyline, anticonvulsants such as carbamazepine, or antiarrhythmics such as lidocaine.
Management of Drugs
Drugs which are considered by the U.S. Department of Justice, Drug Enforcement Agency (DEA) to be controlled substances must be stored in a locked cabinet in a secured area (e.g. behind two locked doors). Controlled substances must never be left unattended since the potential for theft and misuse of these drugs is high. In the past, the DEA allowed some latitude in research facilities and did not closely observe who exactly administered these drugs to the research animal. This is no longer true. Therefore, each investigator with a DEA license must personally supervise the administration of these drugs. In addition, OVR may no longer transfer controlled drugs to research staff.
All drugs, whether or not they are DEA regulated, must be properly labeled and included on the label must be the expiration date. Expiration dates should be checked periodically, at least once every three months, and expired drugs immediately discarded. It is a violation to use expired drugs on animals involved in research procedures (there are a few limited occasions wherein expired drugs may be used for terminal, non-survival procedures). University Animal Care staff will discard any drug they observe to be improperly labeled, or in use after the expiration date has passed. At the minimum the label on a drug shall include:
- name of drug and concentration
- expiration date (also the mixing date if a combination)
- name of Investigator (if the drug is not owned by OVR)
- specific storage requirements (e.g. refrigerate)