Abstract: The present invention is directed to a method of preparing a pharmaceutical dosage form, the method comprising (a) encasing a pharmaceutical dosage form comprising an estrogen in a container essentially impervious to oxygen, and (b) purging the container with an inert gas, and pharmaceutical dosages formed by the method thereof. The present invention is also directed to a pharmaceutical kit comprising (a) a container impervious to oxygen, wherein the container contains an atmosphere of essentially inert gas, and (b) a pharmaceutical dosage form, wherein the pharmaceutical dosage form comprises an estrogen and wherein the pharmaceutical dosage form is encased in the container.