What is Antihistamines Poisoning?
Antihistamines can be found in over-the-counter cold, allergy, and sinus medications. Antihistamines are used by humans to treat a variety of conditions, such as allergies and sinus ailments. Antihistamines may also contain combination ingredients, such as aspirin, codeine, caffeine, dextromethorphan, and pseudoephedrine. Common brands of antihistamines include Dimetane, Zyrtec, Chlor-Trimeton, Tavist, Benadryl, Allegra, and Claritin. If a dog has ingested antihistamines, it will be very important to take the box that contained the medication with you to the veterinarian so the ingredients will be known.
Antihistamines come into categories: first-generation and second-generation. First-generation antihistamines, when taken, have a sedative effect. Many people refer to these as the “older” antihistamines since they can cause marked drowsiness, unlike the second-generation medications. They can also cause blurry vision, dry mouth, difficulty with coordination and concentration, and nausea. The second-generation antihistamines are purchased more often since they are in non-drowsy form; however, if they are taken above the recommended dosage they can still have the same side-effects as first-generation antihistamines.
Antihistamines poisoning in dogs occurs when dogs ingest a quantity of medications, either over-the-counter or prescription, that contain antihistamines. This type of toxicity is treatable if immediate medical attention is given.
Symptoms of Antihistamines Poisoning in Dogs
When dogs overdose on antihistamines, symptoms depend on the quantity consumed. Symptoms of antihistamine poisoning in dogs include:
- Rapid heartbeat
- Irregular heartbeat
- Hyperactivity
- Seizures
- Vomiting
- Confusion
Types
It is important to know the type of antihistamine your dog ingested and the ingredients contained in combination with the particular medication. Differential diagnoses of antihistamine poisoning in dogs include:
- Amphetamine poisoning
- Caffeine poisoning
- Pseudoephedrine overdose
- Alcohol toxicity
- Marijuana toxicity
- Barbiturates or tranquilizer overdose
Causes of Antihistamines Poisoning in Dogs
When a dog consumes antihistamines, depending on the amount ingested, toxicity can occur. Poisoning due to antihistamine overdose is caused by:
- The constriction of the smooth muscles in the respiratory tract
- The increased permeability of the capillaries
- Negatively affects the central nervous system
- Cardiovascular abnormalities
Diagnosis of Antihistamines Poisoning in Dogs
Once you have taken your dog to the veterinarian, he will need to know more information about what the dog ingested. This is why bringing in the box or container of the medication is very helpful. The veterinarian will perform specific laboratory tests, namely blood testing, plasma tests, and evaluations to check the dog’s concentration of serum antihistamine. The veterinarian will also perform urinalysis and possibly a biochemistry profile in order to check the levels of antihistamines in the dog’s system. If the veterinarian is certain that the dog has ingested antihistamines, due to the evidence of the box and your observations of his past consumption, he may rely heavily on his clinical signs in order to determine the mode of treatment.
Treatment of Antihistamines Poisoning in Dogs
Once the veterinarian has made a diagnosis of antihistamine poisoning, he will immediately begin treatment. Treatment methods include:
Emesis
If your dog has already vomited, the veterinarian will not need to induce vomiting. The induction of vomiting may be conducted in order to help rid the dog of the substance. Once emesis has occurred, the dog should display natural gastrointestinal decontamination, or the veterinarian will give the dog activated charcoal to aid in the absorption of any residual toxic substances.
Medications
Medications to suppress the central nervous system may be given, especially if the dog is having seizures. Diazepam is often the drug of choice to control any seizure activity, and there are other drugs that work as well. Medications, namely methocarbamol, guaifenesin, or pentobarbital may also be used.
Monitoring of Systems
The veterinarian will closely monitor the dog’s heart rate, arrhythmia, and respiratory rate. The monitoring of systems also is dependent upon if the animal ingested a medication that has been combined with the antihistamine.
Recovery of Antihistamines Poisoning in Dogs
The prognosis for antihistamines poisoning in dogs is good if treated promptly. Once the dog has shown progression after treatment and recovery, the veterinarian will give you detailed instructions on how to continue to care for your dog at home. Monitoring your dog after treatment is very important; your veterinarian will want to see him again to check his vitals and to be sure that he is recovering properly. Before you take him to the veterinarian for a follow-up visit, if you see any changes in his behavior for any new symptoms it is imperative to contact your veterinarian. In order to prevent antihistamines poisoning in dogs, it is crucial to store all medications in a safe place that is not accessible by the dog for any other pets. Many dog owners choose to store the medications in a box with a lid to further prevent any accidental ingestion.
Antihistamines Poisoning Questions and Advice from Veterinary Professionals
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My 2 year old boxer just got 5 pills of her allergy meds. She is 75 lbs and they are 25 mg tablets of benadryl. She's showing no signs of side effects but i am very worried.
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My 5 month old puppy that is 10-15 pounds cockapoo ate 1 claritan D last nite. This morning he is very agitated, panting, not eAting breakfast or drinking g water and his eyes ate bright red. Help
Claritin D can be fatal to dogs as it contains pseudoephedrine, please take your dog to the vet asap
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Shitzu 14lb gave her 2.5mg of Claritin non drowsy allergy and sinus tablet. No problem last night but tonight she is just staring at the floor and seems confused. Should I be concerned?
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My dog ate approx 2 or 3 tabs of claritan. not sure when. hes 20 lb schnauzer. 9 yrs old. only symptom has been loose stool. He seems fine other than the stool He has had 2 loose movements in a 10 hr time span.
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my 21 lb jack russell ate 180 mg allegra at 7am. it is 2 pm and she appears to be fine. do I need to do anything? I did not think it would harm her. now after reading this article I am concerned. What should I do?
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My approx 13.5 lb chihuahua was accidentaly given a single 10mg certrizine dose instead of a 5mg. I have read the certrizine dose is 0.5 mg per pound but benadryl is 1mg per pound. He seems perfectly fine at the moment and isn't exhibiting any symptoms but I am concerned that as time passes he will. Should I induce vomiting to get it out?
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My pit mix was overdosed. She was given 1 full pill yesterday and 1 full pill today if Claritin -D Walmart brand. It’s non drowsy allergy and congestion relief-d. With pseudoephedrine 240mg and Loratadine 10mg. I got The wrong pills. Since she had been given the wrong dosage and possible the wrong pills, I’m worried. She has a different demeanor, she is panting but not active, she won’t drink water, ears are back as if she’s anxious and her pupils are huge. It’s like she’s high. No vomit or seizures. She is a Pit Mix at 72-78 pounds.
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My dog has consumed her Chlorphen (4mg) by accident. It was supposed to be for 5 days. She took about 12-14 tablets. Should I bring her to the vet? How many days should we observe? She is about 15 kgs. Thanks in advance.
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My puppy takes 25 mg of Benadryl twice a day and I just gave her the nightly dose. My other dog takes zyrtec 10 mg while giving that dog his dose he dropped it from his mouth and the puppy ate that dose of zyrtec also. She is 11months and weighs 40 pounds. Do I need to worry about her?
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My dog ingested one Allegra D 24 hr last night and apparently one late morning today. At 10:45 PM, he is exhibiting hyperactivity as he is walking circles around the house. He is breathing heavier but I feel it is due to the circles. What do you suggest? I checked for elevated heart rate but it is hard to say that it isn't elevated due to the circles being walked. Please advise.
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I gave my pug children’s Claritin (5mg) about 3 hours ago, however she is still very congested. As you know pugs are already at a disadvantage in the respiratory aspect. I typically give her children’s Benadryl, but bought the Claritin by mistake. The Benadryl is used as an alternative to her prescription antihistamine, and given in conjunction with prednisone as needed. I gave her 10 mg of prednisone this morning as well.
Can I give her 12.5 mg of bendryl? Or will it be unsafe. I had scheduled an appointment for tomorrow with our vet to get her prescription allergy medication refilled.
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I just caught one of my dogs chewing on a bottle of otc Claritin. I asked my wife how many she had taken she said maybe 6 or 7 it was a 30 count bottle and I was only able to locate 5 pills. Should I be overly concerned and take him to the emergency vet?
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My dog was caught chewing on a bottle of Claritin 10mg tablets, do not believe and were left. My dog is about 25 pounds. Should there be any concern?
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My dog is 68 pounds and for a long car ride I gave him 75 mgs of Benadryl (3 tablets) with dinner thinking that he weighed more than he did.. he is not exhibiting any signs other than being tired. Should I take him to a vet or will he be okay?
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My son's 1 y.o. ~ 50# Australian Shepherd male accidentally ingested appx. 20 loratadine @ 10mg each. His roommate dropped the bottle and never said anything. Yesterday dog was in agitated state, panting, and motor skills impaired and my son couldn't understand why until he found the empty pill bottle (roommate hadn't said anything). By that time the vet hospital was already closed. He called the local vet this morning and they said just to keep monitoring him. I found it odd they didn't ask to bring him in for an eval of his vital signs and maybe some blood work. Son says dog's breathing is getting better, less agitated, but shouldn't he have been see/treated?
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I accidentally gave my dog a double dose of her allergy medication. She took one dose an hour ago (that I didn’t know my husband gave her) I just gave her the second dose. She takes Cetirizine 10mg 1tab and Chlorphenirimine 4mg 2 tabs. She isn’t showing any symptoms yet. Should I do anything?
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My Pit (4 yrs old) was prescribed to be given Two Benadry pills twice a day (that is 50mg of Benadryl twice a day). This has gone on for many weeks. Other (pain) meds are being taken for knee issues. Within the past couple days, he has begun throwing up bloody vomit and is not eating normal food. His stool is borderline diarrhea in tiny amounts and is very dark brown.
He is sleeping a lot; but not lethargic.