Sir Terry Wogan, the famous broadcaster, is slightly older than me. One of his favourite expressions is: “I am rarely free of pain.” I often feel the same, particularly when getting out of bed or when I have been sitting in a car for some time. I suspect that the majority of the pain is in my joints but undoubtedly there is also pain in my muscles, tendons and ligaments.
The result of this pain is lameness and it is worse in wet, cold weather. Mercifully, I can usually work through it and carry on my life as an equine and farm animal practitioner. This pain is different from that I used to suffer after a hard game of rugby and which definitely got better with time. Many people urge me to take nutrachemicals in the form of joint supplements or pain relief in the form of non-steroidal anti-inflammatory drugs (NSAIDs). I choose not to take any medication in the theory that at the moment the pain is bearable and if I don’t take these medications, they will be more effective should it get worse.
That is my choice. Horses do not have a choice – we have to make it for them. The ultimate choice, if the pain is unbearable, is euthanasia. Most owners do not struggle with the concept of euthanasia when their equine friend has reached the end because of a catastrophic fracture of a long bone. Sadly, the decision is then straightforward. Equally, if a horse is suffering with a treatable condition then normally the decision for treatment is straightforward. What is not so clear-cut is the grey area in the middle. Horse owners and vets have to decide when the quality of a horse’s life is not sustainable from a welfare standard.
In this article, I’m considering chronic skeletal pain in the old horse – not acute pain which occurs normally as a result of an injury in the young horse. Following my analogy, I’m looking at the pain I suffer as a 70-year-old, not the pain I suffered as a 20-year-old after playing rugby. Giving an old horse joint supplements must be good. As far as I am aware, they do not have any bad side effects if given at the manufacturer’s recommended dose.
Correctly formulated supplements must be considered the gold standard, though owners must check that the ingredients can be effective. They must also check that the amount of each ingredient per daily serving meets a horse’s requirements.
There is very little repeatable trial evidence to convince us of their effectiveness, but anecdotal evidence is good. Non-steroidal anti-inflammatory drugs (NSAIDs) can be added and in general, it is acceptable to give these together.
NSAIDs are the most commonly used drugs for control of pain and inflammation in the horse. Dosage rates vary for the mule and the donkey and this scenario should be discussed carefully with your veterinary surgeon. If your practitioner is in any doubt I would refer him or her to The Donkey Sanctuary in Sidmouth, who are very helpful. It should also be remembered that the use of NSAIDs will normally preclude the equine for being slaughtered for human consumption.
The primary action of NSAIDs is via COX inhibition of the inflammatory pathway: in simple terms, by inhibiting enzymes which cause inflammation and pain. Unfortunately COX inhibition may have some detrimental adverse effects. These are complex, but simplistically, they may have detrimental effects primarily on the gastric mucosa (mucous membrane layer of the stomach) and on the kidneys. These side effects often worry horse owners and I can understand their concerns. However, when used at the correct dosage these are very safe drugs which can usually be used at the lower dosage range for prolonged treatment. Unlike antibiotics, which must be given for a full course, NSAIDs can be given strategically so that if the weather is good and the horse is not showing signs of pain, i.e. lameness, the dose can be reduced or the drug can be withheld and only started again if lameness returns. However, I must stress yet again that horse owners have a duty of care. Horses should not be allowed to suffer.
Below is a list of some of NSAIDs used in equine practice. I have used their correct generic names not their trade names so there should be no confusion:
This is the oldest known NSAID. It is available as a powder for administration by mouth. It has a bitter taste, so is not palatable. It has a very short half-life, said to be seven minutes, in the horse. This means there is a large dose required of 100 mg/kg. This large dosage has been used by some practitioners for the control of pain in animals with laminitis. It can be given every other day with phenylbutazone at 4.4 mg/kg being given on the other day to reduced the danger of toxicity. It is also available in tablet form.
This NSAID is useful for musculoskeletal pain. It is available as a solution for intravenous use at the rate of 0.7 mg/kg. As there are 50 mg/ml of solution, this is 1 ml per 70 kg. This can be followed up by granules in the food at the same dose rate. It is supplied in sachets which are a daily dose for 300 kg. It is ideal for single daily dosing and has a high safety margin. It is a moderately effective analgesic and anti-inflammatory agent.
This is an ideal drug for the alleviation of pain and inflammation associated with osteoarthritis and the reduction of associated lameness. Its added benefit is its mode of action, as blocking the inflammatory pathways potentially minimises side effects. Its main disadvantage is it is not available in granular form. It is supplied in a solution of 20 mg/ml. The dosage is 0.09 mg/kg daily, giving a dosage of 1 ml/225 kg. It should be given intravenously. It can also be supplied in paste form.
This is the drug of choice for gastrointestinal pain. It is the most potent NSAID for abdominal pain and is also very effective for ocular (eye) pain. It is not so useful in skeletal pain. It is supplied in a solution of 50 mg/ml. The dosage in the horse is 1.1 mg/kg daily., which works out at 2 ml per 100 kg. It should be given intravenously. It may be given intramuscularly but it is irritant and can cause a violent inflammatory reaction and so this route of administration should be avoided. It is useful in cases of endotoxaemia and can be given at a dose rate of 0.25 mg/kg every eight hours. It is supplied as granules in 10 gram sachets containing 250 mg for oral dosing. In inappetent animals (those who lack appetite) it can be given in paste form. Each 10 grams contains 500 mg of flunixin meglumine.
This is only available for intravenous use in equines. It is supplied in a 10% solution. The dose is 2.2 mg/kg, which works out at 10 ml daily for a 450 kg horse. It is only really useful in abdominal pain. As it is not as potent as flunixin meglumine it is useful as it will not mask surgical colics.
This NSAID is only supplied for oral use in 10 gram sachets of granules. The daily dose is 2.2 mg/kg. It has anti-pyretic (fever-reducing) properties as well as anti-inflammatory and analgesic properties. In my experience it rarely seems very effective. However, a few authorities recommend it.
This potent NSAID is useful for alleviation of inflammation and pain relief in acute and chronic soft tissue and orthopaedic disorders. It is available for intravenous use in a solution containing 20 mg/ml. The dose is 0.6 mg/kg, which works out at 3 ml per 100 kg body weight daily. This can be continued by oral administration of the fluid at the same dose. The oral suspension is supplied with a dosing syringe with weight calibration. This NSAID also is available in paste form.
This is the most commonly used NSAID for musculoskeletal pain and inflammation in the equine. It is commonly called ‘bute’. The initial loading dose of 4.4 mg/kg should be halved as treatment continues. It is supplied as a solution containing 200 mg/ml. This works out at 1 ml per 50 kg. It must be given intravenously as it is extremely irritant if it is given intramuscularly or subcutaneously. It also is supplied in powder and paste form for oral administration. 100 mg and 200 mg tablets are available for dogs and can be used for low doses in small ponies for long-term pain control. Occasionally horses will refuse the medicine in their food. In these cases it is useful to put the medicine in the fridge to reduce the smell.
This formulation is available as granules for oral administration. Its actions are very similar to phenylbutazone. It is claimed to cause less stomach wall ulceration and therefore is particularly useful for long-term medication. The dose is 12.5mg/kg daily for two days for horses and then to reduce to 6.25mg/kg daily. This works out at two sachets twice daily for a horse for two days and it should then be reduced to one sachet twice daily. It would appear to be as potent as phenylbutazone.
The clinician has a dilemma with the use of most NSAIDs in pregnant and lactating mares, and in foals under six weeks of age. None of the drugs mentioned in this list are licensed for these categories of equines. However, in my experience they can safely be given to pregnant and lactating mares. It is just that no recognised trials have been carried out, so clinical judgement must be used. NSAID’s have a very reduced safety margin in young foals and so the author cannot advise their use.
Vets have other possibilities to help alleviate the pain and inflammation associated with osteoarthritis and the reduction of associated lameness in older horses. One such possibility is the intravenous injection of sodium hyaluronate (hyaluronic acid). Recent studies have shown that this drug exerts its lubricant effects primarily on the membrane separating the synovial fluid from the soft tissue (capsule) of the joint. Sodium hyaluronate therefore has various properties:
- It improves the viscosity of the synovial fluid through its 3-dimensional structure (lubrication)
- It assists the filtering function of the synovial membrane (regulation of composition of synovial fluid)
- It is a constituent of hyaline cartilage
Sodium hyaluronate has an anti-inflammatory action. It can safely be used in pregnant and lactating mares. It needs to be given as a course of three intravenous injections at weekly intervals. Courses may be repeated, so if horse owners have their animals on nutrachemicals but further long-term pain relief is needed and they are reluctant to use NSAIDs, this option is open to them.
In conclusion, horse owners should liaise with their vets and their nutritionists to plan a wide-ranging, multi-modal strategy to reduce pain in old horses to an acceptable level. I think we all accept that leaving a chronically lame horse on ‘bute’ for the rest of its life without careful monitoring is not consistent with modern welfare codes.