Fulvestrant is administered using intramuscular injections. For the most part the full effects of the drug can be achieved using 250 milligrams per injection. Due to the active life of the compound these injections only have to be administered approximately once every four to five weeks. This is obviously a benefit when compared to the frequent dosing schedule that is required with aromatase inhibitors or selective estrogen receptor modulators.
At doses of 250 milligrams per month it has been shown that fulvestrant is just as effective as one milligram per day of anastrozole or milligrams per day of letrozole at reducing estrogen in the body.