It might help the experts around here (such a Sqad) if you mention the name of the tranquiliser. Some might work differently to others.
However the general advice seems to be that you should take any sedative tablets you've been given about 1 hour before the procedure. In the absence of any other advice, I'd assume that you're expected to take them together but it might be best to phone the surgery for specific guidance anyway.
douglas - // I was given Valium suppositories years ago but for all the good they did after swallowing them I'd have been as well sticking them up my orifice. //
And a very happy fifty-seventh birthday to that one!!
How long does it take to work? Lorazepam tablets and liquid start to work in around 20 to 30 minutes. It reaches full sedating effect after 1 to 1.5 hours and lasts for around 6 to 8 hours.