Bone Cancer in Dogs
Bone Cancer in Dogs
Pain is the unpleasant sensation that develops with the stimulation of specialized sensory nerve endings, called pain receptors. Pain most often develops from damage, irritation or inflammation of tissues or structures of the body. Pain is a protective mechanism. It causes the animal to react and to move away from the source of the stimulus.
Manifestations of pain are highly variable in animals. Some signs are obviously related to pain, while others are more subtle. The individual personality of the animal and its tolerance for pain also affect the clinical manifestations of pain. Animals in pain often present with a wide variety of signs. Some signs that are associated with pain include the following:
- Altered behavior – quieter than normal, avoidance of other animals or people, hiding, aggressive behavior, fear biting, mental dullness and depression, agitation, restlessness, pacing.
- Altered movement or gait – lameness, reluctance to move, reluctance to get up, wobbliness, abnormal carriage or use of one or more legs, stiffness.
- Vocalization – growling, howling, yipping, moaning.
- Decreased or lack of appetite (anorexia).
Pain management is designed to decrease discomfort and provide maintenance of quality of life. Pain management is directed at the source of pain in order to control it or to change how the dog perceives the pain. There are both medicinal and non-medicinal methods of achieving pain control, and often both modalities are combined in some way to attain the best result possible. Pain management is designed to decrease discomfort and provide maintenance of quality of life.
Amputation provides definitive pain relief. Amputation will restore quality of life, and in many cases, actually extend it, since dogs with severe pain from bone cancer are often euthanized at an early stage to end their suffering. Management of post-operative pain can be successfully achieved with several of the modalities described herein.
Radiation is prescribed for those dogs who cannot undergo amputation, either because of the location of the tumor or because the dog is not healthy enough to undergo surgery. There are two types of radiation: palliative and stereotactic.
In some cases, debulking surgery might be indicated to relieve pressure on vital structures and decrease tumor size. It is not a common procedure for bone cancer, but can be an option for soft tissue or joint tumors. This is done only for palliative pain relief.
Acupuncture & Chiropractic Medicine
These two options are often combined with other modalities. There are many veterinarians who are certified in acupuncture and chiropractic care.
Studies have shown that the continuous use of pain medications is more effective than using them “as needed.” Chronic pain is best managed with stable blood levels of the medication, avoiding a “see-saw” effect when the medicines are only given “as needed.” It is particularly difficult to assess when a dog actually needs the medication, because many of them are stoic and may not exhibit classic signs of pain on a regular basis (limping, decreased appetite, panting, decrease in mobility, etc.). Administering the medications on a regular schedule may also allow for decrease in dosage, because the pain level is also decreased.
Whenever possible, consultation with a veterinary pain management specialist may be extremely helpful in managing the dog’s pain.
Non-Narcotic Pain Medications
Non Steroidal Anti-inflammatory Drugs
These include aspirin and other anti-inflammatory drugs, known as NSAIDs (non steroidal anti-inflammatory drugs). The most commonly used drugs in the NSAID category are carboprofen (Rimadyl®), deracoxib (Deramaxx®) and meloxicam (Metacam®), but others are available as well.
Both the meloxicam and the carboprofen are also available in injectable form. Gastrointestinal (GI) irritation in varying degrees is a common side effect with these medications. To minimize this side effect, stomach-protecting medications are often prescribed in conjunction with the NSAIDs. The most commonly used medications for this purpose are misoprostol and sucralfate. Other medications such as ranitidine (Pepcid®) or cimetidine (Tagamet®) have been used but are not as effective in preventing the GI side effects. These medicines are more effective if used once the damage to the GI tract has occurred. Symptoms can range from nausea and decreased appetite to bleeding in the GI tract. Dark, tarry or bloody stools, or vomiting blood or “coffee ground” material (indicating digested blood in the GI tract) are signs of bleeding in the GI tract and must be reported to the veterinarian immediately.
NSAIDs can also affect kidney and liver function and should not be used in dogs with decreased liver or kidney function, or prior history of liver or kidney disease. Caution is recommended if NSAIDs are being prescribed along with other medications that may affect the liver or kidneys. This should be discussed with your veterinarian. Baseline kidney and liver function tests should be done before the medication is started and should be repeated periodically while the dog is taking the medicine. NSAIDs may affect clotting function by decreasing the way platelets stick to each other (this is known as platelet aggregation). Platelets are little blood cells that stick together to start formation of a blood clot, whenever there is tissue damage. It is important to discuss this effect with the surgeon if any procedure or surgery is planned.
Several herbal medicines may also have anti-inflammatory properties. NSAID side effects may be exacerbated by herbal anti-inflammatory medications and are not recommended to be used together. If your dog is taking any herbal medications, please consult with your primary or holistic veterinarian before combining these medicines.
Tramadol is a centrally acting analgesic that stimulates an opioid receptor in the brain. It is not approved by the FDS for use in veterinary medicine, yet it is widely prescribed as an analgesic. While it may be beneficial as part of a pain management protocol, recent studies suggest that tramadol may not be as effective as previously thought. The most common side effects include sedation, anxiety, panting, dysphoria, agitation, constipation and upset stomach.
Narcotic Pain Medications
Morphine is a well-known drug used to alleviate pain. Although it is not approved for veterinary use, it can legally be prescribed for use as an “extra-label” drug. Morphine can be administered by injection, oral tablets, oral solution and rectal suppositories.
Adverse effects associated with morphine include nausea, vomiting, slowed intestinal movement, constipation, restlessness, low blood pressure, slowed heart rate, slowed breathing, behavior changes and seizures. The most profound adverse effects associated with morphine are suppression of breathing and sedation.
Fentanyl is a very potent opiate narcotic analgesic. It is 100 times as potent as morphine. The fentanyl patches are used for pain control. The patch should NEVER be cut.
The patch should be applied to an area of the dog’s body that cannot be reached by licking or chewing. The pet must be prevented from eating a fentanyl patch. An overdose may result, leading to excessive sedation and depression. The area should be shaved or the hair clipped very close to the skin. Avoid areas that are irritated or otherwise damaged. The skin should be cleansed with alcohol and thoroughly dried before applying the patch. Once applied, the patch should then be held in place for 5 minutes, to allow body heat to activate the adhesive substance. It can be held in place with a bandage if necessary. A skin rash may develop at the site of the patch. The patch is only effective for three days and, if pain persists, the patch should be replaced following strict instructions by a veterinarian. Skin sites should be rotated to minimize accumulation in subcutaneous depots, which could result in erratic blood levels.
The more common side effects include sleepiness, constipation, dizziness and nausea. Less common side effects include difficulty breathing, confusion, tremors, vomiting, decreased breathing rate, and lack of coordination. Rare side effects include hiccups and hallucinations.
Care must be taken when treating an animal with a fever or if using direct heat to the area. Increased body temperature can increase the amount of fentanyl absorbed and lead to overdosing.
Gabapentin and amantadine can also be used as part of a pain management protocol.