a method for administering a pharmaceutical to an animal includes imbibing a plurality of carriers with the pharmaceutical , placing a barrier into the animal , defining a first zone and a second zone within the animal , the barrier permitting passage of the pharmaceutical between the zones and impeding passage of the carriers between the zones , and placing the imbibed carriers into the first zone . also , a method for treating mastitis in a mammal includes imbibing a plurality of carriers with an antibiotic effective in combating a mastitis - causing pathogen , placing a barrier into the udder of the mammal , defining a first zone and a second zone within the udder , the barrier permitting passage of the pharmaceutical and impeding passage of the carriers , and placing the imbibed carriers into the first zone . also , apparatus for administering a pharmaceutical to an animal includes a barrier adapted to permit passage of the pharmaceutical and to resist passage of carriers adapted to reversibly hold the pharmaceutical , the barrier being positionable within the animal such that the barrier may define a first zone and a second zone within the animal , and a plurality of such carriers positionable within the first zone , whereby as the pharmaceutical is released from the carriers it may pass the barrier from the first zone into the second zone .