With medications, whether they are formulated for humans or animals, you have to be extremely careful because your dog’s system is much different from your own. An allergic reaction can happen immediately after dosing, or hours later, so you should always note when your dog has been given a medication or has had a vaccine. This is especially important if your dog has already had an allergic reaction to something else, including food, dander, or grass, to name a few. Although it is not as common as inhalant or contact allergy, medication allergy or adverse reaction is not uncommon, and many cases go unreported because people do not know the cause of their dog’s symptoms. In some cases, the symptoms will be blamed on the condition that is being treated or not noticed at all because dogs spend so much time away from their owners (outside or while you are not home). Just as with any allergy, one of the first signs you will notice is itching, but it will probably be accompanied by vomiting, diarrhea, or sneezing. This type of allergy or adverse effect can lead to anaphylactic shock which results in cardiac and respiratory failure and can be fatal if not treated immediately.
One of the most common causes of death in dogs is due to an adverse reaction to medication. This can happen from giving human medications, such as antihistamine or antibiotic that you may give for an illness or injury, or it could be a medication specifically formulated for animals, like flea treatment. Even when it is a medication prescribed to your dog from the veterinarian, your dog can have an allergic reaction or an adverse effect if you give the wrong dosage. Similar to humans dogs may be sensitive to certain medications like penicillin, and also to products like flea treatment medications.
Another problem could be a drug interaction if the medication is given with another one that, in combination, causes an adverse effect, such as with some medications that already have aspirin in them. If you give your dog aspirin for pain or fever before or after giving that medication, your dog may have symptoms such as vomiting, diarrhea, drooling, and lethargy. In rare cases, your dog may have a reaction to a medication that triggers anaphylaxis, which is a serious condition that can be fatal. This can happen quickly, so it is imperative that you observe your dog carefully after giving any kind of medication. If your dog is suddenly wheezing and having trouble breathing or collapses after giving medication, go to a veterinary hospital right away.