What if you had steven johnson syndrome from a medication that you need to take. can you ever potentially take that medicine again in the future?

Unfortunately, No: you cannot have this medicine again in the future, your doctor will have to seek an alternative. If it were just a severe allergic reaction or even anaphylaxis, and no alternative available, desensitization can be tried by an allergist/immunologist, but in of case of history of SJS caused by the drug, desensitization won't work, the drug has to be avoided, good luck