Interceptor is a prescription medication due to its preventive action against heartworms. There is a shortage of the product at the moment due to a manufacturing problem; Novartis, the producer, has closed one of its factories. If you struggle to find Interceptor you can use Program Plus which is available on our website. There are differences between the products but their heartworm prevention is the same. Please read the information leaflet before starting the treatment and it is advisable to discuss this change with your vet as well.