The pill is to be cut into quarters.
Get a pill cutter if you do not have one and give 1/4 of that pill.
You say you trust your vet, follow their instructions.
I googled it see chart below. One pill would be for a puppy weighing 12 Lbs. you are giving 1/4 of a pill not the entire pill.
Directions:
Each flavored chewable contains 30 mg of pyrantel pamoate and 30 mg of praziquantel. The dose for each drug is 2.27 mg per pound of body weight (5 mg/kg). Please refer to the following dosing table for help finding the right dose for your dog.
VIRBANTEL® Flavored Chewables Dosing Table
Dog Weight
Number of Chewables 6.0 to 12 pounds:...1 Chewable
12.1 to 25 pounds:2 Chewables
More than 25 pounds:Use 114 mg size.
__________________ Joan, mom to Cody  RIP Matese  Schnae  Kajon  Kia  forever in my  A House Is Not A Home Without A Dog |