Martin,
I always worm with Ivomec 1% solution for cattle/swine on the first of the month at 1/10cc per 10 lbs of body weight... this a heartworm preventative.
The following week i'll worm with Safeguard/Strongid paste, about what you put on your tooth brush... this is for intestinal worms. I rotate the Safeguard and Strongid every month.
I know with Panacure it needs to be done 3 days in a row to work. How about the SAFEGUARD?