There are certain health issues your dog may have that warrant the use of a decongestant. Some of these decongestants are also for human use and found over the counter in most drugstores. While there are nasal decongestants that are safe for dogs, it is important to first know which ones they are. Also make sure to discuss medication use with your veterinarian before administering anything to your dog.
Diphenhydramine is an antihistamine used to inhibit histamine, which can cause nasal congestion. Diphenhydramine is found in medicines such as Benadryl and the standard dose is 1 to 3 mg for every lb. of your dog's weight. However, you should clarify dosage with your veterinarian.
Dextromethorphan is found in cough suppressants such as Robitussin, Vicks Formula 44, and St. Joseph Cough Suppressant for Children. According to Pet Education, Dextromethorphan is not approved by the U.S. Food and Drug Administration for use in animals, although it is accepted practice to use this medication in specific cases. Dextromethorphan suppresses the cough center located in the brain without causing sedation, which occurs with narcotic cough suppressants. Only use this medication in dogs that have a non-productive cough, such as kennel cough. Dosage depends on your dog's weight and is best determined by a veterinarian.
Like Dextromethorphan, Guaifenesin is found in cough suppressants such as Robitussin and is also not FDA approved for use in animals, yet is commonly given to suppress non-productive cough due to congestion. The common dosage is 1 tsp. for every 20 lbs., orally every six hours. As with any medication, confirm the dosage with a veterinarian.
Hycodan is the brand name for the narcotic Hydrocodone Bitartrate, used commonly as a cough suppressant. Hycodan works by drying respiratory secretions that often come about in conjunction with nasal congestion. This is a powerful medication only available by prescription. Cough suppression with Hycodan helps with dog health issues such as kennel cough or a collapsing trachea. Your veterinarian must approve this medication for your dog, along with dosage instructions.