Codeine is a pain-killer similar to many others in the market like Morphine or Hydrocodone. It reacts with the chemicals in the brain that send you signals of how much pain you are in and makes them believe that they are in less pain than they are actually experiencing. This means that Codeine basically increases the pain threshold of the patient, even though the pain is still actually there. You can buy Codeine online without prescription if you feel that the pain is getting more than you can handle. Codeine has also been known to have a sedative effect.