I had wanted Minocycline for MS but been refused. But I knew that Minocycline is commonly prescribed for Acne. I had a rash on my body and made an appointment with a dermatologist. I asked the dermatologist for a prescription for Minocycline, which he gave me to treat the rash, and fortunately the dosage was what I wanted (100 m.g. 2x/day.)
I can't remember how long the prescription was good for, but I remember I then quickly made appointments with three neurologists and explained at each appointment that I was already on Minocycline (I did not mention the rash) and needed someone who could take over my care and continue the prescription. I also brought in some supporting literature to the appointments with me. The first two neurologists said no, but the third said yes.
Some neurologists are known for being more flexible than others. But you also have to be prepared with some strong arguments as to why you don't want one of the standard disease modifying drugs (cost, you've tried them and they don't work, the side-effects will interfere with work or child care, etc.) and be persuasive in explaining that the Minocycline is not likely to hurt you (it has been around for a long time, many people have been on it long terms with few side effects, it is inexpensive, etc.)