People typically buy codeine online in various doses depending on their level of pain; consult your physician first before buying more than what's recommended as codeine has FDA (Food and Drug Administration USA) approval. Codeine is an opioid pain medication that's often used to treat mild to moderate pain. It works by changing the way the brain and nervous system respond to pain. However, I read that it's only available by prescription and should only be taken as directed by a healthcare provider. Also, I learned that codeine can be addictive and may cause serious side effects if not taken properly. If you have any concerns or questions about codeine, it's best to talk to your healthcare provider.