MMC is handling all pre-approval communications for Oporia, which is currently under regulatory review.
Paul Ewing, Pfizer's director of PR, said it chose MMC because of the agency's emphasis on communicating with women.
"We selected them because they brought a solid understanding of market dynamics," he said.
MMC executive vice president of healthcare Megan Svenson said this the first time the agency had actually launched a Pfizer drug.
Other Pfizer drugs the agency currently works with include overactive bladder drug Detrol, migraine drug Relpax, and birth control shot Depo-Provera.
If approved, Oporia faces a crowded market. However, Time magazine last year named it one of the most promising drugs for 2005 after studies showed it improved bone density more than Eli Lilly's Evista, a similar product.
Terms of the agreement were not disclosed.
Last week, Pfizer won US Food and Drug Administration approval for depo-subQ provera 104. The medicine is the first new treatment for endometriosis in 15 years and is for managing pain caused when uterus tissue migrates and implants in other areas such as the ovaries and fallopian tubes.