I have been through about 5 wholesaler changes and 1 GPO change (that one was the worst.) I suggest running reports of your Fast movers/High Volume and of your top dollar items and ordering about one additional week of each. We actually had the old wholesaler keep us on for an additional week so I had the option of ordering through both. That can get a little confusing at times but it gives you more options until the new wholesaler gets all of what you need in stock.
I am pretty lucky that all of the wholesalers we have had are close to us here in the Seattle area so we get really great delivery and same day delivery if we need it. I hope this helps some. It's really not so bad.Good Luck
