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For dogs with short or long-term pain, pain patches can provide a real benefit, including avoiding the need to repeatedly give medication to a reluctant patient! The patch was developed for humans and delivers fentanyl, a narcotic or morphine-like drug. Veterinarians prescribe these patches as an “extralabel” pain medication. This means that the patch can be used safely by the veterinary community, but is not officially approved for pets.
The patches come in several strengths, containing different amounts of fentanyl. Dosage is indicated in micrograms (mcg) delivered through the skin—from 12.5 to 100 mcg per hour. This is both helpful, as we can use a patch on virtually any size dog, and convenient, since patches cannot be cut down (the liquid fentanyl would leak out of its container).
The patch is applied to shaved skin, and after a 12- to 24-hour delay, it begins to slowly and steadily deliver the medication through the skin and into the bloodstream. This delay allows us to put the patch on a dog the day before surgery so that it kicks in soon after the end of the procedure. If that isn’t possible, other drugs are used until the patch starts working.
We can also combine the patch with other painkillers. These have to be chosen wisely, as some medications may counteract the patch. A good combination is a non-steroidal anti-inflammatory drug and the patch, each of which treats pain by a different mechanism. Since some patients seem to benefit more from the patch than others, this helps us tailor a pain management plan to each individual. After approximately three days, the patch will be empty and is replaced or removed. Fentanyl is a tightly regulated drug, and your veterinarian will likely ask that you return the patch to the clinic.
At our surgical practice, we’ve used pain patches following surgery of the spine (neck or back), jaw, ear or chest cavity. Repair of a really bad fracture, removal of some types of tumors and limb amputations are also likely situations.
Use of the patch is certainly not limited to surgery patients, however. It’s also appropriate for medical conditions that are especially painful, such as pancreatitis (inflammation of the pancreas) or peritonitis (irritation or infection of the belly). Occasionally, a dog’s pain is managed at home with a patch that is replaced every few days; this typically includes cancer patients, who may experience ongoing or chronic pain.
Like most medications, fentanyl patches can have side effects. Among them are a slow heart rate or sedation, severe breathing difficulties or a very slow breathing pattern (this is rare), euphoria or abnormal excitement, or constipation and difficulty urinating. If such side effects occur, the patch should be removed immediately. Some dogs will develop a rash in reaction to the glue that keeps the patch stuck to the skin; these usually resolve quickly after the patch is peeled off (an ointment with cortisone often helps speed up healing). While most dogs tolerate the patches well, not all do; never hesitate to call your vet if you feel your dog is having a questionable reaction.
The pain patch may also interact with other drugs, such as medications to treat Cushing’s disease, senility and some parasites, so vets weigh the pros and cons on a case-by-case basis before prescribing its use.
Careful supervision is vital when pain patches are used. Fentanyl is highly addictive and there is a potential for abuse—intentional or accidental—by humans. Among the dangers to people is difficulty breathing to the point of suffocation. Children are especially at risk, and some veterinarians refuse to prescribe a pain patch if there is a young child in the family.
Overall, the pain patch is a very useful tool that has dramatically changed veterinarians’ pain protocols. Side effects are generally rare in dogs, and most benefit greatly from the pain relief.