There are many different medicines that start with the letter P. Some of the most common include prozac, prednisone, and penicillin. Each of these medicines has a different purpose and is used to treat a variety of conditions. Prozac, for example, is a common antidepressant that is used to treat depression and anxiety. Prednisone is a corticosteroid that is often used to treat inflammatory conditions such as asthma and arthritis. Penicillin, meanwhile, is an antibiotic that is used to treat bacterial infections. These are just a few of the many different medicines that start with the letter P. With so many options available, it is important to speak with a doctor or pharmacy technician to find the best medication for your individual needs.