What is the ruling on manufacturing and selling anal suppositories for women that increase the weight of the lower body, and are used for the purpose of weight gain, not primarily for treatment, given their natural ingredients and the possibility of a poisonous herb among them?

It is permissible to use beneficial suppositories for medicine and to treat emaciation if you are certain they cause no harm. You must verify this by asking doctors. If harm is found, then selling them is not permissible, due to the Prophet's (peace be upon him) saying: "There should be no harm nor reciprocating harm," and due to the jurisprudential rule: "The basic principle regarding anything harmful is prohibition."