Most horse owners will have experience of administering NSAID or anti-inflammatory drugs to their horse at some point. It is rare to find a horse that has not needed pain relief for any number of conditions, such as injury, colic or laminitis, to name just a few! However, it can be easy to become complacent about their use, given how commonly they are prescribed. In this article we ask what these drugs are and if they are as safe as we would like them to be. 

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What are Non-steroidal anti-inflammatory drugs (NSAIDs)?

These drugs belong to a group used to provide pain relief, reduce swelling and inflammation. In terms of pain, they act to block inflammatory pathways bringing relief from pain. They also have the ability to treat endotoxaemia. Endotoxaemia is a condition that may arise as a result of colic or sepsis, such as retained placenta, amongst other conditions. The earliest commercially produced NSAID was aspirin. Interestingly, the active agent in this drug is salicin; which is found in the bark of the willow tree, used by humans 3500 years ago for the relief of fevers or pain! 

These drugs act on a group of receptors known as COX. The COX enzymes are responsible for pain, fever and inflammation, and the NSAIDs act to reduce this response. They are called non-steroidals to distinguish them from steroids, which can also reduce inflammation, but act in a different way. 

The most commonly used NSAID for horses in the UK is phenylbutazone, often known as Bute

This is usually administered intravenously by a veterinary surgeon or orally as a paste or powder by owners or carers. Like all licenced NSAIDs, it can only be prescribed by a veterinary surgeon. It is also worth noting that before prescribing or using phenylbutazone, the veterinary surgeon must check your horse’s passport to ensure that it has been signed to declare that the horse will never enter the human food chain. We have NSAIDs that are licenced for food producing animals. But they can be more expensive in some cases, but offer a good alternative if your passport is not available or in certain conditions. 

Are NSAIDs safe?

Administration of an NSAID, like most drugs, can result in toxicity. It has been established that phenylbutazone is one of the more likely NSAIDs to induce toxicity in the horse. The risk of toxicity is dependent on a number of different factors; such as health of the horse, hydration status or the concurrent administration of other drugs. Your vet will weigh up all these clinical parameters when deciding whether or not an NSAID is necessary for your horse or indeed which NSAID is most appropriate or not for your horse. Not all NSAIDs are the same, for example, some are more appropriate for foals or for horses with gastric ulceration.

Toxic effects are usually seen in the kidneys or in the gastrointestinal system

In the early stages, signs of toxicity may be vague and non-specific such as inappetence, intermittent colic, depression or increased water consumption. Some cases may show signs of oedema or swelling in the lower abdomen. In advanced cases, the horse may have diarrhoea, dehydration and have a low blood pressure and poor circulation.

Clinically, in healthy horses, on the recommended dose of NSAIDs, toxicity is unusual. However, any horse receiving drugs should be carefully monitored. Dehydration or concurrent nephrotoxic drugs are the main risk factors for renal toxicity in the horse, so if your horse is not drinking, you should contact your veterinary surgeon before administering phenylbutazone. You should also make a veterinary surgeon aware of any drugs that have been given to your horse so that they can decide if it is safe to administer an NSAID at that time. A common example is if your horse is receiving phenylbutazone regularly for laminitis and is seen by a veterinary surgeon for colic, your vet will usually ask about any drugs so that they can alter the dose of NSAID that they may give to treat the colic symptoms. 

NSAIDs can be extremely helpful in keeping horses with chronic orthopaedic disease comfortable long term, whether that be in retirement or for light work

As veterinary surgeons, we regularly see an improved quality of life in older horses prescribed NSAIDs. In some cases, other therapies such as joint medication, physiotherapy, acupuncture, farriery or weight loss may be useful to reduce lameness without the need for NSAIDs.  In the UK, when prescribing long-term drugs such as phenylbutazone, vets are obligated to carry out a clinical assessment of your horse before a repeat prescription. The time frame between examinations can vary, but is usually around 6 months. Although as an owner, this can seem frustrating, and an added expense. But it is very important that your vet checks your horse to make sure that there are no subtle early signs of problems developing which may necessitate a change in protocol or drug. 

In summary, when used in appropriate cases, at the correct dosage, NSAIDs are very effective

They are frequently used long term, in cases such as osteoarthritis, or laminitis, but they can cause side effects. It is vitally important that your horse is carefully monitored and reassessed before and during administration of these drugs. Your veterinary surgeon will be able to advise on the suitability of these drugs for your horse as well as other drug or treatment regimes that may be helpful in addition to or as an alternative to NSAIDs. 

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