OsPhos Now Available

Credit: OsPhos Courtesy Dechra

For years we have heard about the wonder drug Tildren and its ability to make horses with navicular syndrome, hock arthritis and ringbone go sound. Until recently, Tildren was not available in the United States. Just a few weeks back, that changed when CEVA, the manufacturer or Tildren, gained FDA approval for its use in the United States. But did you know that drug manufacturer Dechra also recently came out with a competitor to Tildren? It is called OsPhos and it is showing some promising results!

What is OsPhos?

OsPhos is an injectable bisphosphonate solution for the control of clinical signs associated with navicular syndrome in horses four years and older. OSPHOS inhibits bone resorption (disappearance) by inhibiting cells called osteoclasts. Osteoclasts grab onto calcium crystals which comprise bone and dissolve them. By stopping osteoclast activity, OsPhos slows bone degradation. Sound familiar? That is because this drug has the same mechanism of action as Tildren. See how they compare here.

Does it work?

Clinical trials conducted by Dechra in order to comply with FDA testing requirements found that 75% of horses treated with OsPhos showed a significant reduction in lameness by 56-days post injection. Here is a more direct way of putting it: horses that were grade 3 out of 5 lame (3= lame at a trot in the straight line) pre-OsPhos ended up being only a grade 2 out of 5 lame (lame at a trot in a circle but sound in a straight line) two months post administration. More information can be found here in the FDA freedom of information summary on OsPhos.

Are there side effects?

Nothing significant to speak of. One in 10 horses showed signs of abdominal discomfort (pawing, fidgeting, cramping) about 2 hours post-injection, but got over it after a 15 minute walk. Some were given a dose of banamine but none had serious or lasting reactions. More information can be found here.

How is it given?

OsPhos is administered as three 5 cc intramuscular injections given in three locations on the body all at once. It can be given every 3 to 6 months depending on the severity of the lameness, but ultimately should only be repeated as needed when signs of lameness recur. In other words, some horses may only need it once, while others many need it two or three times per year.

How does is stack up to Tildren?

In many ways, OsPhos holds its own against Tildren:

  • OsPhos is currently available through veterinary supply distributors while Tildren is on backorder.
  • OsPhos costs about $300 to $350 per treatment while Tildren will usually run around $1,100 to $1,300.
  • OsPhos can be given intramuscularly while Tildren has to be given intravenously. In addition, Tildren has been reported to be most efficacious when it is diluted in a bag of IV fluids and administered over a period of hours. This requires a catheter and more time under veterinary supervision while it is being given.
  • OsPhos shows similar results to Tildren in terms of reduction in lameness and in time of onset. Tildren definitely exerts a long term effect, with many owners reporting that it reaches full performance 3 months following administration and continues to work for years thereafter. Because OsPhos is so new, we will have to wait and see how it measures up to Tildren over the long haul.

No matter how you look at it, OsPhos is a welcome addition to the horse world in the U.S. If it can help our horses be more comfortable, while saving us some time and expense, then pop open the champagne!