My cat requires a liquid medicine for a fungal infection she contracted several years ago (treatment can last for years). During the course of her treatment we've switched back and forth between two medications with no problem in acquiring the new one. I've even called and talked to the pharmacist when I had a question about the medicine separating (high concentration means it doesn't stay mixed - he recommended storing it on it's side so it's easier to shake it up). Roadrunner has been a life saver (literally). It's easy to order refills online and shipments are fast. Also, they include a free toy with each shipment which are enjoyed by all our cats. I am so grateful Roadrunner Pharmacy.