No, I didn't start it until well after I finished the doxycyline. The whole reason I started it was because the doxy left me with horrible gastritis. I had the cimetidine on hand because I've taken it for PCOS symptoms in the past. I started researching the drug's anti-androgen effects (because my breasts grew a cup size in one month - bonus), then stumbled upon the research in shingles, HSV, and CFIDS. I continued to take it daily (or every other day) and had wonderful results. That's when I came here to share with you fine people.