Are long term painkillers safe for my horse?

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 nonspecific 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 longterm 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