Common causes for coughing in dogs can include: A upper respiratory infection (bacterial and/or viral), Asthma, Bronchitis (caused by infection or allergies), Heart disease (an enlarged heart will apply pressure on the lungs), Pneumonia, and Heartworm disease
Giving a basic cough suppressant/expectorant can be okay, but must be used carefully. Some people will give it, see improvement, but the pet is not improving. It is simply covering up the symptoms.
To ease coughing, you can give Dextromethorphan, which can be found over-the-counter. However, many cough medications over-the-counter are combination products. So, if you grab a product like Robitussin, make sure it doesn’t have other ingredients like acetaminophen or caffeine. If it also contains Guaifenesin that is okay.
The dose is 0.25 to 0.5 mg per pound of body weight every 8 hours.
So, a 20 pound dog could get anywhere from 5mg to 10mg of dextromethorphan.
If at anytime your pet is panting heavily for hours, has difficulty breathing or excessive coughing, regardless of the cause, please contact an ER veterinarian immediately.
Hope that information helps