I don't know whether you can transmit giardia via dogs or people, generally these are water-borne pathogens so you might want to consider your water source.
Those things should do the trick, the first drug you took is for worm, Metrodiazole is a very common anti protozoa drug. Giardia is not a super bug in the protozoa world show they should fall. Enteric coated oil of oregano and the myrrh/goldenseal combo from nature's way would help as well.
If those things fail consider Rifaximin (have to order overseas such as MagicPharma.com) will do the trick. Are you sure you have giardia?