L drugs that suppress things like nausea/vomiting/diarrhea are as a class generally things that dull stimulation of nerve pathways. They calm the symptom and also can cause other side effects like drowsiness, weakness constipation, urinary retention etc. differing from drug to drug a little, but the side effects are from calming things too much in other areas, like the smooth muscle of the bowels might be "calmed" to the point of constipation.
L'hermittes is a sensitivity of the nerves in the neck area to movement that sends a tingling washing down the body, particularly stretching when you put your head down toward your chest, I assume this is what you refer to? Any drug that dulls nerve exictability will probably help with that symptom ( any of the antiepileptics for example ), but the side effect profile may not be welcome in every day life!
All drugs that we use therapeuticlly have unintended side effects, sometimes it turns out to be something you want!