It can take two to six weeks for clindamycin phosphate to begin producing results and up to 12 weeks for it to produce a complete benefit in clearing acne, according to WebMD. If acne does not improve within this period, contacting a doctor to discuss further treatment is recommended.
Clindamycin phosphate is an antibiotic that helps diminish acne by preventing the growth of bacteria that causes it, according to WebMD. A topical medication, clindamycin phosphate is used by applying a thin layer of the lotion to the affected areas. Some common side effects to this medication include burning, itching, peeling skin and redness.