The main ingredient in Epiduo is Benzoyl Peroxide. In addition to Benzoyl Peroxide, Epiduo contains Adapalene (Differin) which is very irritating and most probably does not add a lot to the efficacy of the product. Clindamycin is a topical antibiotic. Unfortunately, most acne bacteria are resistant to topical antibiotics (learn more about the risk of topical antibiotics for acne here). Nevertheless, Clindamycin is not irritating and that can be used in addition to Benzoyl peroxide (or Epiduo). Thus, if you already have bought Epiduo you can use it instead of regular benzoyl peroxide.