FDA warns about risk of possible accidental overdose of dogs treated with Sileo

This article has been updated to include a statement from the manufacturer.

The United States Food and Drug Administration (FDA) is warning veterinarians and dog owners about the risk of accidental overdose to dogs treated with Sileo, according to an agency release. Sileo (dexmedetomidine oromucosal gel), manufactured by Zoetis, is a prescription gel given to dogs by mouth to treat noise aversion (signs related to anxiety or fear due to noise).

The drug is packaged in an oral dosing syringe with a ring-stop mechanism on the plunger that must be "dialed" and locked into place in order to set the proper dose for the dog. Overdose can result if the ring stop isn't fully locked. The FDA stresses it's very important that the person administering the product understands how to operate the syringe correctly before giving the product to the dog.

Zoetis began marketing Sileo in May 2016. Since then the FDA has received 28 reports involving overdoses in dogs due to the ring-stop mechanism not properly locking at the intended dose. In some cases, the release states, the entire contents of the dosing syringe were administered to the dog. In 15 out of 28 cases, dogs experienced clinical signs of overdose, which include lethargy, sedation, sleepiness, slow heart rate, loss of consciousness, shallow or slow breathing, trouble breathing, impaired balance or incoordination, low blood pressure and muscle tremors. No deaths have been reported.

At this time, the agency has not determined if the overdoses were due to improper use of the ring stop. Veterinarians and pet owners should be aware of the possibility of accidental overdose if the Sileo syringe isn't properly locked before dosing. The FDA strongly encourages veterinarians and their teams to provide education in proper operation of the syringe and the potential signs of overdose to dog owners before dispensing the drug. It's also important to advise pet owners to contact their veterinarian if they see any of these signs.

In a statement, the manufacturer says, "We at Zoetis take these reports seriously. The health and well-being of animals is our highest priority. As with any prescription medication, it is important for pet owners to fully review the instructions to ensure proper administration to a pet. So that dogs fully benefit from Sileo, we encourage veterinarians to discuss with pet owners how to use the syringe and administer Sileo. We also encourage pet owners to review the step-by-step dosing instructions that are included in the Sileo package and the instructional videos available online on the Sileo product website (www.sileodogus.com)."