There's no question that dogs feel pain. But because they are the descendants of wolves, they often attempt to hide their pain to avoid showing weakness. Since they have different degrees of stoicism and tolerance to pain, it can sometimes be challenging to pinpoint the source of the pain.

Only when we identify subtle signs of the pain can we provide relief from discomfort. Less-than-obvious signs include excessive panting, shivering, rapid breathing, a rapid heart rate, elevated body temperature, and frequent changing of position while lying down or sitting. Dogs with ear infections may shake their heads or scratch their ears frequently. They may also lick and chew at painful areas, which might be mistakenly interpreted as itchiness. Since dogs don't necessarily volunteer what degree of discomfort they're experiencing, it's up to owners and veterinarians to figure it out and address the problem appropriately. This is especially true for dogs that have undergone surgery.

Any major surgical procedure that involves entering a body cavity (such as the chest or belly) or cutting into bone warrants pain control medication in some form. The most painful surgeries are those that involve bone penetration, and veterinarians give pain medications before these surgeries, as well as afterwards. The length of time after surgery that pain control is needed is variable. If healing is expected to be prolonged, as with many bone repair procedures, pain relievers are usually administered for several days.

Pain control in dogs is important not only for humane reasons, but also because adequate pain management facilitates a more rapid recovery.

This is especially important in the immediate post-operative phase as a dog is awakened from anesthesia. It helps the dog have a smoother, and in many cases, more rapid recovery. Dogs that have their pain well managed will progress quicker to eating, drinking and getting up to relieve themselves. In addition, these dogs are more likely to be sent home sooner.

Owners need to exercise discretion and common sense, however, when using pain-control drugs for their dogs after surgery. They can actually be harmful to the patient if the dog is feeling so little pain that he tries to resume normal activities too soon. Dogs should be discouraged from too much activity and may even need to be confined until a substantial amount of healing has taken place. This is certainly true for patients that have undergone bone surgery.

Traditional means of pain control in dogs involves the use of pain-relieving (analgesic) drugs. Generally, the most common analgesics used by veterinarians for dogs fall into one of four categories: Non-steroidal anti-inflammatory drugs (NSAIDS), corticosteroids, local anesthetics, and morphine-derived narcotics.

NSAIDS are a large group of analgesic drugs that include aspirin and carprofen, among others. These drugs interfere with some of the biochemical pathways that cause swelling, and in so doing, contribute substantially to pain control. These drugs are useful in controlling mild to moderate pain. But dogs tend to be very sensitive to them and caution in dosing is important in order to avoid stomach ulcers and problems with kidney function.

Corticosteroids are another distinct group of drugs that are very potent anti-inflammatories. They include such drugs as prednisone, dexamethasone, triamcinolone, and others. Corticosteroids can be given in a variety of different ways such as: into a vein, under the skin, into the muscle or joint spaces, or orally. They're also available as short-acting or long-acting preparations, which adds to their utility. Corticosteroids do have an array of side effects in dogs such as increased drinking, eating, and urination, and can even cause thinning skin and a pot-bellied appearance if used long-term. These effects are reversible, however, and steroids remain a very important group of anti-inflammatory medications for more chronic situations. They're not generally useful for post-operative pain relief.

Local anesthetics act by blocking the nerves that conduct pain sensations to the central nervous system. They're very effective in controlling pain, although their effects are generally short-lived. These drugs must be given locally in the region where surgery is being performed. Also, they block nerves that control muscle use, so the dog may not be able to move about well while they're in effect.

Morphine-based drugs are the most potent analgesic drugs available for use in dogs. These narcotics have no anti-inflammatory properties like the drug classes previously discussed, but rather they interfere with the perception of pain on a neurological level. They generally have no lasting side effects, but they're extremely powerful and careful dosing practices are essential. They can be given orally, intravenously, or by injection.

The narcotic drug fentanyl acts similarly to morphine, but can be given with a transdermal patch that's applied to the skin with an adhesive. Narcotics are most effective if given before the pain starts, so they're often given preoperatively. They have the added benefit of causing drowsiness and decreased activity.

Morris Animal Foundation is supporting a study by Dr. Kris T. Kruse-Elliott of the University of Wisconsin School of Veterinary Medicine. Dr. Kruse-Elliott and her colleagues are investigating the analgesic power of transdermal fentanyl versus administration of morphine in the spinal canal before surgery (called "epidural" administration). Among other important objectives, the veterinarians conducting the study will evaluate the length of analgesia provided by these different means of narcotic administration for dogs undergoing bone surgery. The study results will help veterinarians choose the most appropriate route of administration for pain control drugs in dogs that require bone surgery.

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Rob Hilsenroth, DVM, is Executive Director of Morris Animal Foundation. This nonprofit organization sponsors animal health studies at veterinary schools and institutions throughout the U.S. and in other parts of the world. All annual unrestricted contributions to the foundation support health programs -- not the cost of administration or fund-raising. If you'd like to make a contribution, write Morris Animal Foundation, 45 Inverness Drive East, Englewood CO 80112. For more information, call (800) 243-2345 or visit http://www.morrisanimalfoundation.org/