There are many different medicines that start with the letter O. Some of these medicines are used to treat common conditions like headaches, nausea, and colds. Others are used to treat more serious conditions like cancer and heart disease. Still others are used to prevent illnesses like malaria and rabies. No matter what the condition, there is likely a medicine that starts with the letter O that can help. So if you’re ever feeling under the weather, be sure to ask your doctor about an O-medicine that can help you feel better soon.