If you are on Medicare, and reach the doughnut hole, you can obtain free prescriptions from most of the pharmaceutical companies. Find the website for the company – if it is not on the bottle, either search on Google, or ask your pharmacist.
They usually have a Patient Assistance section with an application form and directions. It is worth getting the paperwork prepared early – you have to get a prescription from your doctor, and it can take 6 weeks or so to get your free prescription. There are limitations on some of the prescriptions – you might have some out of pocket expenses – but they will be considerably less.