depends on...
how bad your acne is. If it is very bad, go with Accutane, suggested above. If it is moderate to intermitten, I'd use topical products such as prescription strength Benzoyl Peroxide wash and lotion (8% BP), or Differin gel (adapalene - see differin.com). There are others, but these have worked reasonably for my back and chest acne.
BTW, even if the working hypothesis surrounding the use of tetra/doxy -cyclines states that it is thru inhibiting protein synthesis, that's enough for me to stay away while on cycle. I'm spending like $10-15 per day on gear and ancillaries, and I'm not gonna screw that up with some cheap prescription antibiotic just to kill some zits. JMHO, tho.
later,
DrG