Tiludronic acid

Tiludronic acid (INN; also known as tiludronate) is a bisphosphonate used for treatment of Paget's disease of bone (osteitis deformans) in human being medicine. It has the tradename Skelid. In veterinary medicine, tiludronic acid is used to treat navicular disease and bone spavin in horses. Its tradenames are Tildren and Equidronate. It is approved for treatment of navicular disease and distal, tarsal osteoarthritis in Europe,^[1] and was approved for treatment of navicular disease in the United States in 2014.

Tiludronic acid

Clinical data
Trade names	Skelid
AHFS/Drugs.com	International Drug Names
ATC code	M05BA05 (WHO)
Legal status
Legal status	CA: ℞-only
Identifiers
IUPAC name {[(4-Chlorophenyl)thio]methylene}bis(phosphonic acid)
CAS Number	89987-06-4 Y
PubChem CID	60937
IUPHAR/BPS	7604
DrugBank	DB01133 N
ChemSpider	54905 N
UNII	6PNS59HP4Y
KEGG	D08599 N
ChEMBL	ChEMBL1350 N
CompTox Dashboard (EPA)	DTXSID10237966
ECHA InfoCard	100.121.105
Chemical and physical data
Formula	C7H9ClO6P2S
Molar mass	318.60 g·mol−1
3D model (JSmol)	Interactive image
SMILES c1cc(ccc1SC(P(=O)(O)O)P(=O)(O)O)Cl
InChI InChI=1S/C7H9ClO6P2S/c8-5-1-3-6(4-2-5)17-7(15(9,10)11)16(12,13)14/h1-4,7H,(H2,9,10,11)(H2,12,13,14) N Key:DKJJVAGXPKPDRL-UHFFFAOYSA-N N
NY (what is this?)  (verify)

Mechanism of action

Tiludronate is a non-nitrogenous bisphosphonate that inhibits osteoclasts, the primary cell responsible for the breakdown of bone required for bone remodeling. Non-nitrogenous bisphosphonates are metabolized by osteoclasts to compounds that then replace a portion of the adenosine triphosphate (ATP) molecule, making it non-functional. These non-functional molecules then competitively inhibit ATP in the cell, reducing cell energy and leading to apoptosis.^[2] Decreased levels of osteoclasts subsequently reduce the degree of breakdown of bone and bone turnover. Non-nitrogenous bisphosphonates are less potent than nitrogenous bisphosphonates.

Relative potency^[3]

Bisphosphonate	Relative potency
Etidronate	1
Tiludronate	10
Pamidronate	100
Aledronate	100-500
Ibandronate	500-1000
Risedronate	1000
Zoledronate	5000

Use in equine medicine

Tiludronate has been used primarily for the treatment of diseases in horses that are associated with inappropriate osteolysis, such as navicular disease^[4] and osteoarthritis. It has specifically been shown to improve lameness in horses with osteoarthritis of the distal hock joints (bone spavin)^[5] and vertebral column.^[6]

Method of administration

Tildren is administered intravenously. It is labeled for 0.1 mg/kg dosing, once daily for 10 days by slow intravenous injection, which for a 500 kg horse works out to be 1 vial per day. However, one study giving all 10 doses at once (1 mg/kg IV as a single CRI) was found to have the same pharmacological effects, and is used clinically.^[7] It may be given systemically or locally, by regional limb perfusion. Although RLP is thought to have certain benefits, including decreased cost and reduced risk of adverse effects, some diseases must be treated systemically, such as osteoarthritis of the vertebral column. Systemic administration is often given by adding a 1 mg/kg dose into a 1-liter fluid bag, which is slowly given over 60–90 minutes. Its effects are reported to last 4 months or longer, with a peak effect 6–8 weeks post treatment.^[8] The effects of regional limb perfusion has come into question due to in vitro studies showing that high doses given by RLP or intraarticular injection may damage articular cartilage by chondrocyte apoptosis.^[9] Further studies are needed to evaluate the safety of Tildren administration via RLP.

Adverse reactions and contraindications

Tildren has been shown to have several adverse effects.^[10]

• Signs of colic, which is usually self-limiting, occurs in 30-45% of horses.
• Tachycardia
• Electrolyte disturbances: primarily calcium, magnesium, and potassium, which can last for several hours. Caution should be used in horses with disease processes that could be affected by electrolyte disturbances, such as hyperkalemic periodic paralysis or cardiac disease.
• Kidney damage: it is eliminated by the kidney and is not recommended for use in animals with impaired renal function.
• Less serious reactions include stiffness of the neck, decreased appetite, fever, and increased urination.

It is not recommended for animals under four years of age, due to lack of studies evaluating its safety in growing animals, nor for pregnant or lactating animals, since its effect on the fetus has not been studied.

References

1. Kamm L, McIlwraith W, Kawcak C (2008). "A review of the Efficacy of Tiludronate in the Horse". Journal or Equine Veterinary Science. 28 (4): 209–214. doi:10.1016/j.jevs.2008.02.007.
2. Rogers MJ, Crockett JC, Coxon FP, Mönkkönen J (July 2011). "Biochemical and molecular mechanisms of action of bisphosphonates". Bone. 49 (1): 34–41. doi:10.1016/j.bone.2010.11.008. PMID 21111853.
3. Tripathi KD (2013-09-30). Essentials of medical pharmacology (Seventh ed.). New Delhi. ISBN 9789350259375. OCLC 868299888.{{cite book}}: CS1 maint: location missing publisher (link)
4. Denoix JM, Thibaud D, Riccio B (June 2003). "Tiludronate as a new therapeutic agent in the treatment of navicular disease: a double-blind placebo-controlled clinical trial". Equine Veterinary Journal. 35 (4): 407–13. doi:10.2746/042516403776014226. PMID 12880010.
5. Gough MR, Thibaud D, Smith RK (July 2010). "Tiludronate infusion in the treatment of bone spavin: a double blind placebo-controlled trial". Equine Veterinary Journal. 42 (5): 381–7. doi:10.1111/j.2042-3306.2010.00120.x. PMID 20636772.
6. Coudry V, Thibaud D, Riccio B, Audigié F, Didierlaurent D, Denoix JM (March 2007). "Efficacy of tiludronate in the treatment of horses with signs of pain associated with osteoarthritic lesions of the thoracolumbar vertebral column". American Journal of Veterinary Research. 68 (3): 329–37. doi:10.2460/ajvr.68.3.329. PMID 17331024.
7. Delguste C, Amory H, Guyonnet J, Thibaud D, Garnero P, Detilleux J, et al. (April 2008). "Comparative pharmacokinetics of two intravenous administration regimens of tiludronate in healthy adult horses and effects on the bone resorption marker CTX-1". Journal of Veterinary Pharmacology and Therapeutics. 31 (2): 108–16. doi:10.1111/j.1365-2885.2007.00936.x. PMID 18307502.
8. Allen KA, Johns S, Hyman SS, Sislak MD, Davis S, Amory J (December 2010). "How to Diagnose and Treat Back Pain in the Horse" (PDF). AAEP Proceedings. 56: 384–388.
9. Duesterdieck-Zellmer KF, Driscoll N, Ott JF (October 2012). "Concentration-dependent effects of tiludronate on equine articular cartilage explants incubated with and without interleukin-1β". American Journal of Veterinary Research. 73 (10): 1530–9. doi:10.2460/ajvr.73.10.1530. PMID 23013178.
10. U.S. Food and Drug Administration. "FDA Provides Equine Veterinarians with Important Information about TILDREN and OSPHOS for Navicular Syndrome in Horses". Retrieved 3 January 2015.

External links

• Prescribing information for Skelid
• RxList page
• tildren.com