In which route is a solution typically administered as a douche?

A douche is a therapeutic method commonly used to introduce a solution into the vagina for cleansing or medicinal purposes. The vaginal route is specifically designed for such applications, where a liquid solution is administered to cleanse the vaginal area or to treat infections.

In contrast, the otic route involves administering solutions into the ear, which is not appropriate for douching. The rectal route involves inserting solutions into the rectum, mainly for purposes like enemas or medications, rather than douching. The ophthalmic route pertains to the administration of solutions into the eyes, typically for eye care or treatment of eye conditions, which also does not relate to douching practices.

Given this context, the vaginal route stands out as the correct answer for where a solution is typically administered as a douche.