Toxicity to pets When accidentally ingested by dogs and cats, antihistamine poisoning can result in clinical signs of severe agitation, lethargy, sedation, aggression, abnormal heart rate, abnormal blood pressure, vomiting, diarrhea, inappetance, seizures, respiratory depression, and even death.
If your dog is prescribed antihistamines you will need to try them for 2-3 weeks to see if it helps. If it doesn't, you'll need to stop giving it to your dog and try another until you find one that works, following the advice of your vet.
Benadryl can be dangerous for your dog if you give too much. An overdose of Benadryl can cause seizures and other side effects. The safest way to give Benadryl is to give it according to the weight of your dog. AKC says the dose for Benadryl is 2 to 4 milligrams per kilogram of body weight, two to three times per day.
Zyrtec is active for up to 24 hours, so your dog will be free from a runny nose, itchy skin, sneezing, and other symptoms for the whole day.
Feeling drowsy or sleepy is one of the most common antihistamine side effects, especially in regard to first-generation antihistamines.
Sedating antihistamines can cause many short-term effects such as urinary retention, constipation, dry mouth, increased appetite, and worsen narrow-angle glaucoma via their action on cholinergic receptors. However, most side effects are mild and stop when the drug is no longer used, or the dose is reduced.
Is it safe to use antihistamines every day? In general, most of the available over-the-counter antihistamines are safe for long-term use. There are some potential side effects and there are some cases where long-term antihistamine use can worsen urinary retention or narrow angle glaucoma.
fexofenadine (Telfast®) – this is a second gen. It is available as 60 mg capsules and 120 or 180 mg tablets. The dose is 5–10 mg/kg once or twice daily (don't use if your dog is on ketoconazole or a macrolide antibiotic)
You can safely give Zyrtec to your dog up to 20 mg per day.
While there's no set timeline for when someone should stop taking an antihistamine, one should speak to a doctor or drug rehabilitation specialist if they feel like they have become addicted to your antihistamine. The severity and length of an antihistamine withdrawal will depend on the specific drug.
However, it can have lethal consequences if given to a dog. It overstimulates their central nervous system and heart, causing canine seizures, heart failure, and potentially death.
To sum it up, all first-generation H1 antihistamines should be taken close to bedtime or when you're able to sleep. Second-generation H1 antihistamines and H2 blockers can typically be taken at any time of the day. One exception to this is cetirizine, which can cause drowsiness for up to 14% of those who take it.
Official answer. Yes, most people can take antihistamines every day, if they have daily symptoms of their allergies.
Antihistamines. Medications such as diphenhydramine (Benadryl) and doxylamine (Unisom) can contribute to rhabdomyolysis and acute kidney injury.
Claritin and Zyrtec are effective and safe for most people with minor allergies.
A nonprescription oral antihistamine, such as loratadine (Alavert, Claritin, others), cetirizine (Zyrtec Allergy, others) or diphenhydramine (Benadryl Allergy, others), may help relieve itching.
Toxicity to pets
When accidentally ingested by dogs and cats, antihistamine poisoning can result in clinical signs of severe agitation, lethargy, sedation, aggression, abnormal heart rate, abnormal blood pressure, vomiting, diarrhea, inappetance, seizures, respiratory depression, and even death.
Fexofenadine, commonly known as Allegra® or Telfast®, is a second generation antihistamine drug that may be used for dogs and cats to control itching and other signs related to allergic conditions.
You may be wondering whether Claritin or Zyrtec is the best pet allergy medicine—but which antihistamine works best for you depends on the severity of your symptoms. For example, a person with a mild allergy to cats or dogs may do well with Claritin. Another person with more severe allergies may do better with Zyrtec.