We got a call from the vet saying our dog has giardia and they gave us metronidazole 100mg for him to take twice a day. It says take it until gone - but it is ALOT of medicine and with the small dosage it will be forever before he is done. Anybody's pet been on this medicine? He's so small, we are quite worried about him. Pepper is a pek-a-poo and is about 6 pounds - 3 months old.