The purpose of this study is to demonstrate the efficacy of Adapalene 0.1% / Benzoyl Peroxide (quoted as BPO) 2.5% Gel associated with Doxycycline Hyclate 100 mg Tablets compared to Adapalene 0.1% /Benzoyl Peroxide 2.5% Vehicle Gel associated with Doxycycline Hyclate 100 mg Tablets, in the treatment of severe acne vulgaris. The safety of the two treatment regimens will also be evaluated.