Hello - I am Dr. Matt - I would be glad to help you with your question.
I am very sorry to hear that she has a very bad cough today. I am glad to hear that you are taking her to your vet though as this is the best way to determine the exact cause and give her the proper medication to relieve her cough.
The most common causes of a cough in dogs are:
- Heart disease such as a weak valve or valvular disease
- A collapsing trachea which is more common in smaller breed dogs - this is basically where the trachea is made up of a very flimsy cartilage that folds or collapses when she is breathing faster
- Allergic bronchitis
- Mild pneumonia from bacteria or fungal infections
- Kennel Cough on an infection of the trachea/bronchi
At this point, as long as she is not having any labored breathing, I do think that waiting until tomorrow should be safe. Your vet will be able to examine her and possibly take an x-ray of her chest to determine the exact cause. For now if you wanted to give her something you can use some Robitussin DM very safely. The dose for dogs is 1/2 of a teaspoon for every 25 pounds every 8 hours. This can cause some drowsiness but is otherwise very safe.
Hope this helps to answer your question - if not or if you have any more questions please feel free to reply. Thank you for your question.