Part 4: NSAID Use in Horses - Pain Management
In our 4th article on Managing Pain in Horse we are going to concentrate on the specific pain medication known as non-steroidal anti-inflammatories or more commonly “NSAIDs” (pronounced en-seds).
In Australia, non-steroidal anti-inflammatories are a type of medication that require a veterinary prescription. This is for very good reason, which we will cover in this article.
What are non-steroidal anti-inflammatories?
NSAIDs are the most common drugs used to eliminate pain and fever in equine medicine i.e. they possess anti-inflammatory and antipyretic properties.
They are known as the first line strategy to combat pain, before other pain relievers such as opioids and natural anti-inflammatories are considered.
For many situations they are the best option for pain management in horses.
The most common NSAIDS used in equine medicine include:
- Phenylbutazone (bute, PBZ)
- Flunixin
- Meloxicam
- Ketoprofen
- Aspirin
- Firocoxib
How Do NSAID Medications Work?
NSAIDs work to eliminate inflammation and fever by blocking the cyclooxygenase (COX) enzymes in the arachidonic acid cascade.
When these COX isoenzymes are blocked, the production of prostaglandins, prostacyclins and thromboxanes are reduced resulting in an effect that can either be beneficial or harmful.
The COX isoenzymes have different functions.
- COX-1 isoenzymes are continually expressed by many tissues and are involved in the formation of cellular protective prostaglandins in the gastric mucosa (stomach lining), regulation of renal blood flow and platelet aggregation (necessary for blood clotting).
- Blockage of COX-1 enzyme activity can result in less desirable side effects such as gastric ulceration, kidney damage and bleeding disorders.
- Conversely, COX-2 isoenzymes are only expressed when stimulated to do so by inflammatory stimuli and are not present in normal, healthy tissue.
It therefore stands to reason that NSAIDs that block COX-2 activity are said to have reduced side effects.
Side Effects Of NSAIDS
While the vast majority of horses handle these anti-inflammatories just fine, there are specific situations when complications are more likely.
Pre-existing conditions such as gastric ulcers, dehydration, toxaemia and concurrent use of other nephrotoxic drugs can predispose a horse to an increased risk of an adverse reaction when given these medications.
Overdosing, particularly in foals and ponies, giving a loading dose for a pro-longed time period or mixing classes of NSAIDs can also result in grave consequences.
It is possible to see the following adverse effects even when using the drug appropriately:
- Gastric ulcers
- Oral ulcers
- Right dorsal colitis
- Renal papillary necrosis (death of kidney tissue)
- Colic
- Diarrhoea
For this reason, it is essential that before choosing an NSAID for your horse the veterinarian must evaluate not only the type of NSAID, but the disease state the horse is in and any sensitivity to the drug that particular horse may have.
Sometimes, it can be very difficult to know how a horse will react to a medication and we should never be blasé when medicating our horses. What can be acceptable NSAID use in many horses, could be a potential death sentence in another.
COMMON USE SITUATIONS FOR NSAIDS
By far the most common use of NSAIDS in the horse is for pain associated with musculoskeletal disorders.
This includes conditions such as:
- Arthritis
- Joint pain
- Muscle strain or penetration
- Hoof conditions
- Bone fracture
Traditionally, flunixin has been the drug of choice for colic pain i.e. pain associated with visceral structures such as the abdomen, bladder and reproductive tract.
Final Considerations
We cannot emphasis enough that use of NSAIDs is not without risk. When your vet is considering what class of NSAID to use as pain relief for your horse they are thinking of the following:
What the cause of the pain/inflammation is eg. Mechanical vs visceral
- 1
Is the pain/inflammation acute or chronic?
- 2
Does the horse have any known sensitivities?
- 3
Are there any concurrent medications being given?
- 4
What is the expected duration of treatment?
- 5
Is the horse competing and will drug with-holding periods need to be considered?
It’s also worth noting that sometimes the chosen NSAID is ineffective at controlling pain and inflammation in some horses. If this is the case it is worthwhile switching to a different class of NSAID.
If your horse is being medicated with an NSAID and you are concerned about NSAID toxicity, please contact your veterinarian immediately.
Note: This is Part 4 of a 4-part series on Managing Pain in Horses. Below you can find links to the other 3 articles.
