Newf Friends can definitely use Doxycycline. We have been experiencing a large number of dogs with Heartworm and we use the Doxycycline as part of the treatment plan.Jen...Do you know if Newf Friends has a need for an unopened shipment of Doxycycline? I bought it from a Canadian online pharmacy and never opened it as my dogs treatment plans had changed by then. If so, I could bring it with me to Newfstock.