Re: High CPK --- possibly myositis? Neuro says maybe....
If the symptoms decrease after the 1st month of antibiotics, I would suggest continuing for at least a month or two after the symptoms are gone. Past that, if the symptoms continue to re-occur and the antibiotics help, you may need a more open ended therapy with them. The good news is that they are quite cheap, about $70/month Cdn.
However, if it is an infection, treating it sooner is more likely to reduce long term consequences.