Best thing you can do is obviously get such a tiny dog to the emergency Vets. If however, there is some reason you can't get to a professional, I would try to get some salt water down the dogs throat. This will act as an emetic and will hopefully make him sick-up most of the tablet.
I would definitely take the dog to the vet, a dog of that size and weight, ingesting a pill that strong can be very deadly, if not destroy his/her kidneys and liver. Good Luck.
Get to the vet and give her some milk so that it dilutes the pill and make sure you give plenty of water to stay hydrated and this will also dilutes the pill good luck
I have an eight pound Chihuahua same thing happened with a 300mg wellbutrin xl tablet. I called my vet (shes awesome) I gave her a teaspoon of household peroxide and she barffed up the pill almost immediately :) fyi :) Now I have my pills in the washroom , and close the door when I take it , so this can never happen again !