My 2 Yr. Old Standard Poodle Has Been Diagnosed With

My 2 yr. old Standard Poodle has been diagnosed with Giardia and has been on medication to kill this disease. Although he still has the Giardia. Is there any type of medication that you have had with excellent results. I can not have him around my little baby and toddler. He has had two rounds of Metronidazole 250 mg and also 3 tubes of Flagyl which he threw up repeatedly. Have you any suggestions for us we are desperate to get rid of this disease for health of both our poodle and family.