While there are many different medicines that start with the letter N, some of the most common include naloxone, naproxen, and naltrexone. Naloxone is an emergency medication used to reverse the effects of an opioid overdose. Naproxen is a nonsteroidal anti-inflammatory drug used to relieve pain and inflammation. Naltrexone is an opioid antagonist used to treat alcohol and drug addiction. While these are just a few of the many medicines that start with the letter N, they are some of the most commonly prescribed.