There is always a danger when a person is prescribed a pain killer. For one, there is a limit to what the body can take when it comes to pain. For another, pain killers cannot be used for long periods of time. Between these two risks, there is also the matter of addiction to pain killers. The temporary release from pain is a welcome feeling. On top of that the patient yearns for freedom from the pain.
This is the first step in getting addicted to prescription pain killers. This makes for a compelling reason for the use of medicinal marijuana.