Recent research has shown that tiludronate, a drug that modifies bone metabolism, is beneficial in the treatment of navicular disease.
Navicular disease is a common cause of lameness. Medical management is based on corrective shoeing and reduction of pain, with or without the use of vasoactive drugs. Recent progress in imaging techniques shows the importance of soft tissue changes, and so the emphasis in recent years has switched towards soft tissue lesions. The bone is often involved, but, to date, there has been little research into the use of drugs which affect bone metabolism.
Professor Jean-Marie Denoix of the CIRALE ( Centre for Imaging and Research into Equine Locomotor Disorders), France, coordinated the clinical trial, which involved researchers in France, Germany and Italy. Fifty horses with navicular disease were included in the study. They were chosen on the basis of clinical signs consistent with navicular disease. All had moderate to severe lameness affecting one or both fore feet, and showed a positive response to pressure over the frog. The lameness was exacerbated by extending the distal inter-phalangeal (coffin) joint with a wedge under the toe when weight-bearing. The lameness improved when the posterior digital nerves were anaesthetised. Horses were only included if changes to the navicular bone were apparent on radiographic examination.
Thirty-three of the horses had signs which had only been apparent for less than 6 months. Seventeen were more long-standing. Horses less than 2 years old, those with fractures or those that had been treated previously with corticosteroids were excluded from the study. No change in pattern of shoeing was permitted during the trial.
Tiludronate is a bisphosphonate - a bone metabolism regulator - which inhibits bone resorption. Bone is a very dynamic tissue, constantly being formed and reabsorbed through-out a horse's life. In the healthy adult skeleton the rate of bone turnover is balanced. If the balance is disturbed, disease can occur. New bone is formed by cells called osteoblasts; while cells called osteo-clasts are involved in reabsorbing bone.Tiludronate acts by inhibiting osteoclast activity.
The researchers divided the horses into three groups. The first group received tiludronate intravenously at the rate of 0.1 mg/kg/day for 10 days (total dose 1mg/kg). The second group were given the same daily dose, but for five days only (total dose 0.5mg/kg). The third group received a placebo. They examined each horse at the end of the treatment period, and then at 1, 2 and 6 months after the end of the treatment.
An interesting feature of the study was the use of video-recording of the lameness examinations. All the recordings, and the radiographs, were reviewed by Prof Denoix. This allowed for consistency of assessment, despite the fact that the study was carried out in several centres.
The results of fifty cases were analysed. Over the whole follow-up period, positive progress was noticed in both treated groups. There was a regular increase in the number of horses that were not lame or were only slightly lame. Horses receiving the full ten days of treatment responded better than those treated for only five days. After six months 75 of them had returned to their normal level of activity. Horses on the lower dose, showed only a temporary improvement. There were no differences in radiographic signs after the treatment The response also appeared to be better in those horses that had been treated within 6 months of becoming lame. Only 25 of the chronic cases were considered to have improved.
Prof Denoix concluded "The results support the medium and long term efficacy of tiludronate in the treatment of navicular disease at a dosage of 1mg/kg. This research opens the way for a new approach for the treatment of equine locomotor disease."
The drug is currently licensed, in France, for the treatment of bone spavin. The cost of a course of treatment for navicular disease would be about 400 euro.
Source: British Equine Veterinary Association Meeting. London. March 2002.