Typically, Pexion takes several days to weeks to work for anxiety. However, this may vary depending on your dog’s metabolism, the severity of their anxiety and the use of other medications and lifestyle changes. it's normally recommended to start it at least two days before a known stressful event. If you think Pexion isn’t working or is taking too long to work, speak to your vet about what else could be done or the alternative medications on offer.