I've been prescribed this after being hospitalised with HG & a different anti sickness pill not working (can't remember what it was called).
This medicine was recommended by the gynae department at the hospital & I was reassured by 3 of the gynae doctors that it is safe & has been used for years. They can't do studies on pregnant women, as its unethical, but it is not a new drug & has been used without problems.
For me, I have no choice but to take this. If i did not take this I would not be able to keep liquids down, which would damage me & therefore baby. I was reluctant to take medicines dying first trimester, but had no choice.
It does not help the nausea much, but has reduced my vomiting - I now vomit just once on waking, not each time I eat or drink.
Bare in mind that uncontrollable vomiting does not have to last long to make a woman dehydrated & therefore lead to hospitalisation & problems. So it depends whether your wife can keep liquid down, not how long she has had it. Being hospitalised for dehydration is not fun, so if you can take pills now to avoid it, that is what I would do.