Doxycycline
"I started a cycle of doxycycline last June because of my horrible summer breakouts.  I experienced dramatic results after about 6 weeks; my skin had never been clearer.  I stopped taking it after 8 weeks and experienced  a few pimples here and there.  It is now February and I'm pretty much back to square one with my acne. I started back on doxycycline last week.  Best advice I can give: be patient, it takes a while but you'll eventually see great results."