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Joint Medication: Part 4 - Systemic joint therapy



So far we have looked into what makes up a joint, joint communication and medication which is injected directly into the joint. Many horses suffer from discomfort in multiple joints. In these cases, there is often a need to treat the horse systemically, therefore treating all the joints simultaneously. This can be done through systemic medication or dietary supplements. A detailed supplement blog will soon follow.


Systemic medication

  • Oral

  • Non-steroidal anti-inflammatories

  • Equipalazone (Bute)

  • Danilon

  • Paracetamol

  • Intravenous

  • Hyaluronic acid

  • Intramuscular

  • Polysulfated glycosaminoglycans

  • Adequan

  • Pentosan Polysulfate Sodium

  • Cartrophen

  • Osteopen

  • Arthropen

  • Intravenous or intramuscular

  • Bisphosphonates

  • Osphos

  • Tildren


 

Non-Steroidal Anti-inflammatories (NSAIDs)


The basic nonsteroidal anti-inflammatory drugs (NSAIDs) function is to stop pain. There are 3 different classes of NSAIDs, based on which part of the inflammation pathway they actually stop, however, this also has a knock on effect in terms of side effects.

The most commonly used NSAIDs for musculoskeletal diseases are:

  • Phenylbutazone - ‘Bute’ - most commonly sold as Equipalazone - this is within the 1st group, called the COX-1 inhibitors.

  • Suxibuzone - Most commonly sold as Danilon - this is a prodrug of Bute, meaning that it is transformed into phenylbutazone once it is absorbed.

Danilon is considered to be more palatable than Bute (1), and have less side effects (2). Bute is mainly associated with the potential to cause gastric ulcers, however, long term use at high levels can also cause kidney disease.


Most importantly, both Bute and Danilon are considered to have the same pain relieving effect (1). Bute has a withdrawal period of 7 days as per the FEI List of Detection Times.


Other, safer NSAIDs also exist. Meloxicam can also be used to treat chronic musculoskeletal disease (3), however, it is not as effective as Bute (4).


Paracetamol

The actual drug in paracetamol is called acetaminophen. This drug does not work through COX inhibitors (unlike the NSAID group). It can therefore be used at the same time as NSAIDs to control discomfort, especially in episodes of acute (sudden) pain (5). Repeated dosing with paracetamol is considered to be safe, with mild changes in liver parameters and no increase in gastric ulceration (6).

Most cases of arthritis and joint pain are not acute and sudden lameness should be discussed with your vet. Paracetamol, however, can be part of your horse’s pain management plan.


 

Hyaluronic Acid (HA)


HA is a non-sulfated glycosaminoglycan. The 3rd part of the blog series showed that intra-articular medication (direct injection into the joint) with hyaluronic acid did not result in significant improvement. Another method of administering HA is intravenously, meaning that it is injected directly into the vein.


Injection of HA into the vein leads to an increase in its concentration in the blood for less than 3 hours (7). Different formulations of HA are commercially available, based on how heavy (the molecular weight) the HA compound is. Heavier HA formulations (above 5 x10ʌ5) are much more effective (8).


This doesn’t seem like a long time, however, scientific studies show that three weekly injections of 40 mg HA decreased lameness and improved the synovial membrane (9).


This also takes us back to the study mentioned in the 3rd part of this blog series:

‘A 2021 study (10) of TB horses with middle carpal joint lameness showed that horses which received PAAG (Arthramid) had an 83% chance of being lameness free at 6 weeks, as opposed to 27% that received TA and 40% that received HA. This is a great case study as all the horses were in flat race training and the lameness was localized to the same joint in every horse.