When I was a public health nurse, I had a young patient who was pregnant for the third time in less than 3 years. I asked her if she used any birth control and she said that we took birth control pills. I asked her to bring them to me so that we could talk about what she was doing, the dosage and whether or not she needed to change to another type of birth control.
With that, she went to the bedroom and came back with . . . vaginal foaming pills (about the size of a Necco wafer). She said, "I've been taking them just like the doctor told me - every time I have sex I take one. They're hard to swallow but I manage."
I sat there for a moment trying to control the hysterical laughter that was rising and ready to burst out of me. I had visions of those foaming tablets bubbling up out of her mouth. I finally grasped onto my professionalism and said in a somewhat stifled (but controlled) voice said, "You were supposed to insert those vaginally every time you had intercourse - not swallow them."
Her reply was, "Now I know why they didn't work." Needless to say, I had some teaching to do and a new form of birth control to get for her!!