I could find no evidence to support it's use in treating/preventing urinary tract crystals, but vets sometimes use drugs as off label medications, meaning they use them to treat conditions not listed on the label.
However, physicians may prescribe other SSRIs in younger patients in an off-label use of these drugs.
Even though Botox has only been approved to treat axillary hyperhidrosis, physicians can legally use Botox "off-label" to treat other affected areas of the body.
Other adult type 2 diabetes medications, such as sulfonylureas and meglitinide drugs, which work by increasing insulin production, may be prescribed off-label for pediatric use.
Off-label use-Prescribing a drug for a population (e.g., pediatric) or condition for which it was not originally approved by the U.S. FDA.