Tessalon Perles (benzonatate) is a medication intended for human use and is not safe for dogs. Giving your dog medication meant for humans can be very dangerous and potentially fatal.
If your dog is coughing, it's essential to contact your veterinarian immediately. They can properly diagnose the cause of the cough and prescribe the appropriate medication for your dog.
Never administer human medication to your pet without consulting a veterinarian.