Pain is complex and there are multiple potential therapeutic targets
NSAIDs are generally considered the foundation of pain management for dogs with arthritis based on the extensive amount of research showing their efficacy and safety in dogs, but sometimes other pain relievers may be considered instead of or in addition to NSAIDs. Your veterinarian might consider recommending Librela, which is an injectable pain reliever, and you can read more about this new treatment here.
What is important to understand about pain is that it is very, very complex. There are many molecules and receptors involved in transmitting a signal from the joint or tissues, to the nerves, up the nerves to the spinal cord, and then to the brain where the signal is perceived as pain. Crucially, if these pain signals are allowed to go unchecked, the nervous system literally starts to remodel so that it becomes easier and easier for the pain signals to get through. When this happens, sometimes signals that are not actually related to pain (such as petting or brushing) trigger the brain to think it is feeling pain. This is a very maladaptive process and highlights that fact that pain is a disease in its own right. When managing arthritis pain, we aim to reduce the signals from the joint so that the subsequent remodeling does not occur- this is how NSAIDs and anti-NGF mAbs (Librela) work. But there are many other points along the pain pathway that can be targeted to reduce pain. Importantly, the remodeling of the nervous system has the potential to be reversed, if and only if, the pain signals are adequately controlled.
This article will review some of the other oral pain relievers your veterinarian might recommend for your dog. CARE cannot make any recommendations or prescriptions for your dog and it is always essential that you talk to your veterinarian about what is appropriate for your dog before starting any new medication.
Amantadine
Amantadine blocks a receptor called NMDA in the spinal cord. These receptors play an important role in the harmful changes that can occur in the spinal cord due to regular negative stimuli from peripheral nerves.
A clinical trial found that using amantadine in addition to NSAIDs led to a significant improvement in activity level, compared with dogs who received NSAIDs alone.
If your dog is currently on NSAIDs for chronic pain, adding amantadine could likely help them move around more easily.
Talk to your veterinarian about whether amantadine might be beneficial for your dog. Side effects are uncommon but could include agitation, flatulence, and loose stools/ diarrhea, particularly at the start of amantadine usage.
Gabapentin
Gabapentin prevents the release of the neurotransmitter glutamate and may reduce neuropathic pain. Neuropathic pain may be experienced in some dogs with arthritis. Gabapentin may also decrease anxiety. We know that pain makes does more anxious, and anxiety makes pain worse, so reducing anxiety is an important part of controlling arthritis pain.
While gabapentin is often prescribed for dogs with arthritis, there is actually no research that has been done to show that gabapentin is effective or safe in dogs with arthritis.
If it is used, gabapentin should be given three times a day to maintain steady blood levels. But, it often causes sedation, especially when dogs are first started on it. It can also cause ataxia (wobbliness), especially in older dogs, and agitation. Your veterinarian may recommend starting with twice a day and working up to 3 times/ day to try to reduce side effects.
One of the best uses of gabapentin is as a pre-visit pharmaceutical, along with trazodone, to reduce anxiety and stress associated veterinary visits.
Pregabalin
Pregabalin is similar to gabapentin in that it blocks the release of neurotransmitters. Two potential benefits of pregabalin are improved bioavailability (the amount of the drug that enters the bloodstream) and a longer half-life. What this translates to is that pregabalin only needs to be given twice a day.
There are no studies of pregabalin in dogs with arthritis. There are studies in dogs with other types of neuropathic pain. Side effects are similar to gabapentin.
Tramadol
Tramadol used to be prescribed routinely by veterinarians to treat chronic pain. However, after more research became available, it appears that tramadol is not an effective pain reliever for the majority of dogs with arthritis because the amount that is able to be absorbed after oral dosing diminishes significantly after just one week of regular doses. There may be some dogs do respond to tramadol, but it appears that in the majority of dogs it is not effective for long term use.
Acetaminophen (Tylenol)
Acetaminophen does not significantly reduce inflammation but is sometimes used to minimize pain. However, no studies have been done specifically looking at acetaminophen use in dogs with arthritis.
Many veterinarians treating chronic pain will recommend acetaminophen for dogs with arthritis or other types of severe pain (ie, bone cancer). It is often a good option for “break through” pain or “flares”- which are expected to occur in dogs with arthritis.
IMPORTANT: ACETAMINOPHEN (TYLENOL) MUST NOT BE GIVEN TO CATS AS IT CAN CAUSE FATAL LIVER DAMAGE. The mechanism that causes toxicity in cats is not present in dogs, however, it is typically advised to avoid use in dogs with poor liver function.
Codeine
Codeine, which is a type of oral opioid, is not considered highly effective for managing chronic pain from arthritis in dogs, partly because it’s poorly absorbed by the GI tract.
However, there are no studies that have specifically looked at codeine in dogs with arthritis. It may be used to treat chronic pain when other pain relievers are incompletely effective or cannot be given. It is sometimes mixed with acetaminophen (Tylenol 3).
Amitriptyline
Amitriptyline is an antidepressant that might help reduce the anxiety that accompanies chronic pain, as well as potentially having some anti-inflammatory effects. It can be helpful for dogs with anxiety or for chronic neuropathic pain.
Venlafaxine
This is the drug with brand name Effexor which is used in people to treat depression; chronic, neuropathic pain, and osteoarthritis.
In dogs, it’s mainly been used for behavior problems but some veterinarians are starting to use it for chronic pain from arthritis as well.