Let me tell you a bit of my history with minocycline.... I first took it at about age 21. I saw improvement within 6 weeks, total clearness after about 4 months or so. The derm then took me off it. Quick results ... ah, those were the days. It was like a miracle cure.
I was mostly clear until age 26, when acne again reared its ugly head, pardon the pun. The derm tried topicals but the acne persisted, so he put me on mino again. This time the acne was worse and took longer to disappear. Not too many zits, but the ones I had were big and persistent (I don't think they were cysts, though), and mild bacne. I was on 100 mg 2x a day for probably a year, then I was on a maintenance dose of 100 mg 1x a day for probably another 2 years. The derm wanted to wait until I was totally clear.
Everything finally cleared and the derm decided to take me off completely. After about 6 months off the bacne came back with a vengeance. So I'm on it again mainly for that. I've been on it for about 8 months now. Face great, back still not so good -- though I think this has to do more with working out and sweating than the effectiveness of the mino.
I know there are risks with long-term use but I've had no adverse effects as far as I can tell. I'm a female but I do not want to go on any form of birth control. The derm is looking to wean me off the mino as soon as possible, but is waiting for the bacne to improve.
Tummy, it takes time, maybe 2 months wasn't enough for you.