Question:
We all know that cocaine is known as an illegal drug. We have also heard of studies where cocaine is included in medication for sick people. Would a person who takes such medication be sinning or become a drug addict?

Answer:
An example we are more familiar with is giving morphine to patients with terminal cancer to relieve constant, intense, excruciating pain. (Perhaps cocaine is used for the same purpose.) If one is terminally ill, he probably will not survive long enough to become addicted.

If one is having intense pain but is not terminally ill (such as following surgery or an injury), one should ask their physician about the potential for addiction if the physician prescribes a narcotic like morphine for pain.
When Jesus was suffering on the cross, He refused to take the gall (a sedative) offered to Him (Matthew 27:34) so as to experience to the fullest degree possible the judgment of God for our sins. If we are experiencing intense pain, it is our privilege to refuse painkillers—especially potentially addicting ones—so that we can experience just a little of what Christ suffered for our sakes (Philippians 3:10). But if we cannot stand the pain and relief is available, it surely would not be sinful to accept a pain-killer or sedative.