Diphenhydramine Toxicity | Poison Control

Take Home Points

• Diphenhydramine is a common cause of anticholinergic toxicity
• Recent internet phenomenon have led to increased misuse of diphenhydramine especially among adolescents
• Physostigmine is a safe and effective antidote for anticholinergic poisoning
• Call the Utah Poison Control Center at 1-800-222-1222 at any time 24/7 for assistance in managing anticholinergic toxicity and administering physostigmine

The U.S. Food and Drug Administration released a warning in September 2020 regarding the dangers of taking more than the recommended doses for over-the-counter Benadryl® (diphenhydramine) allergy medication.¹ Reports of adolescents overdosing on diphenhydramine has drawn national attention.² Teenagers and young adults have been participating in the “Benadryl Challenge” on TikTok, where they post videos of themselves taking large quantities of diphenhydramine. This fad was brought into the media spotlight in more recent months, but diphenhydramine has been one of the most common intentional ingestions even prior to the trend.

Diphenhydramine is a peripherally and centrally acting first generation h2-antagonist with anticholinergic, antitussive, antiemetic, and local anesthetic properties.³ The antihistamine is a lipophilic drug, which allows it to readily cross the blood-brain barrier. Additionally, there is concern for diphenhydramine’s cardiotoxic effects that derive from sodium and potassium channel blockade at higher doses.⁴

The toxicities associated with diphenhydramine are dose dependent. Common signs and symptoms of overdose include confusion, urinary retention, tachycardia, blurry vision, dry mouth, irritability, and hallucinations.² Diphenhydramine-induced QRS widening and QTc prolongation can be seen on an electrocardiogram. With ingestions greater than 1 gram, diphenhydramine may result in delirium, psychosis, seizures, coma, and death. ⁵ There is an even greater risk of seizures, coma, and death when ingestions are greater than 1.5 grams of diphenhydramine.⁶ Fatal deaths have also been reported with oral doses greater than 20 mg/kg.³

Antilirium® (physostigmine), as a true anticholinergic antidote, should be strongly considered for diphenhydramine-induced delirium and agitation. Administration of physostigmine can potentially prevent a patient from being intubated and/or receiving copious amounts of sedatives, including benzodiazepines and antipsychotics. The fear of physostigmine comes from early case reports that resulted in two deaths after overdosing on tricyclic antidepressants and receiving the physostigmine.⁷ Hence, physostigmine is contraindicated in tricyclic antidepressant overdose.³ Such patients are not suffering anticholinergic delirium and instead require resuscitation with fluids, pressors, benzodiazepines, and sodium bicarbonate. Thus, physostigmine should be avoided in patients with a widened QRS, AV block, or bradycardia. Under these circumstances, physostigmine may worsen conduction disturbances, and cause bradyarrythmias or asystole. Precipitation of seizures is another concern for physostigmine.³ This can be avoided by diluting each physostigmine dose of 0.5 to 1 mg in 10 mL D5W or normal saline and administering as a slow IV push over 2 to 5 minutes.³

Physostigmine is very safe when given to patients with anticholinergic delirium. A retrospective cohort study from 2003 to 2012 on patients who received physostigmine found the following adverse event rates: none (95.3%), emesis (2.1%), QTc prolongation (1%), seizure (1%), and death (0.5%).⁸ The death was not temporally related to physostigmine administration. When compared to benzodiazepines, physostigmine is far more effective in reversing agitation and delirium (87% for physostigmine vs 24% for benzodiazepines).⁹ Overall, physostigmine improves anticholinergic delirium in the majority of patients with few adverse events.

Other treatment modalities for diphenhydramine overdoses include sodium bicarbonate for QRS widening.³ The anticonvulsant of choice for treating seizures from diphenhydramine are benzodiazepines, not physostigmine. There is also anecdotal evidence for the use of IV lipid emulsion and extracorporeal membrane oxygenation in severe cases.^10,11

Diphenhydramine is an antihistamine that can cause life-threatening complications in the setting of overdoses. In mild cases, patients may experience anticholinergic toxidrome. Severe symptoms include delirium, psychosis, seizures, coma, and death. Fatal cases have been reported with ingestions > 20 mg/kg. Physostigmine should be considered for diphenhydramine-induced delirium and agitation. Recent literature indicates that physostigmine improves anticholinergic delirium with few adverse drug reactions. Health care providers should be aware of the toxidrome behind diphenhydramine overdoses and promptly identify appropriate treatment modalities.

References

1. FDA warns about serious problems with high doses of allergy medicine diphenhydramine (Benadryl). https://www.fda.gov/drugs/drug-safety-and-availability/fda-warns-about-serious-problems-high-doses-allergy-medicine-diphenhydramine-benadryl. Accessed 8/26/2021.

2. Dangerous ‘Benadryl Challenge’ on Tik Tok may be to blame for the death of Oklahoma teen. KFOR News. https://kfor.com/news/local/dangerous-benadryl-challenge-on-tik-tok-blamed-for-the-death-of-oklahoma-teen/

3. Olson, K.

   Poisoning & Drug Overdose. New York, NY. McGraw-Hill Education; 2018.

4. Zareba et al. Electrocardiographic findings in patients with diphenhydramine overdose. Am J Cardiol. 1997 Nov 1;80(9):1168-73.

5. Diphenhydramine. Lexi-Drugs. Lexicomp. Wolters Kluwer Health, Inc. Riverwoods, IL. Available at: http://online.lexi.com

6. Radovanovic et al. Dose-dependent toxicity of diphenhydramine overdose.

   Hum Exp Toxicol. 2000 Sep;19(9):489-95.

7. Pentel P, Peterson C. Asystole complicating physostigmine treatment of tricyclic antidepressant overdose. Ann Emerg Med. 1980;9(11):588-590

8. Arens et al. Safety and effectiveness of physostigmine: a 10-year retrospective review. Clin Toxicol (Phila). 2018 Feb;56(2):101-107.

9. Burns MJ, Linden CH, Graudins A, Brown RM, Fletcher KE. A comparison of physostigmine and benzodiazepines for the treatment of anticholinergic poisoning. Ann Emerg Med. 2000 Apr;35(4):374-81. doi: 10.1016/S0196-0644(00)70057-6. PMID: 10736125.

10. Labarinas et al. Extracorporeal Cardiopulmonary Resuscitation After Diphenhydramine Ingestion. J Med Toxicol. 2018 Sep;14(3):253-256.

11. Cherukuri et al. IV Lipid Emulsion Infusion in the Treatment of Severe Diphenhydramine Overdose. Am J Case Rep. 2019 May 29;20:758-763.​​​​​​​

​​​​​​​Author: Mark Nguyen, PharmD, Emergency Medicine and Critical Care Pharmacist, Intermountain Medical Center & Michael Moss, MD, Medical Director, Utah Poison Control Center

Benefits, Dosage, Risks, Safety, Side Effects

• Healthy Pets
• Healthy Dogs
• Reference

• View Full Guide

Written by WebMD Editorial Contributors

Reviewed by Amy Flowers, DVM on February 14, 2021

In this Article

• Allergy Relief Without Benadryl

Dogs are curious and energetic, so it’s inevitable that some of them will wind up in some sticky situations. From running through some poison ivy to getting stung by a bee, there are plenty of problems that can lead to your dog feeling itchy, uncomfortable, and swollen from an allergic reaction. 

Your dog doesn’t need to suffer, though. With a vet’s guidance, you can use diphenhydramine (Benadryl) to ease the worst of their allergy symptoms. Here’s how Benadryl can be given to dogs safely. 

Benadryl, or diphenhydramine, is an antihistamine that helps relieve the symptoms of allergies in both humans and animals. It can also be used to relieve the symptoms of motion sickness if a dog needs to be transported long distances. For most dogs, the appropriate dosage of Benadryl is perfectly safe. It will begin to reduce symptoms like skin rashes in about an hour. 

Getting the dosage right is important because most Benadryl tablets are intended for humans. Some dogs can be quite small, so they need less Benadryl than a person. Dogs also metabolize Benadryl differently, so it’s not a good idea to rely on human dosing guidelines.  

Benadryl dosage for dogs. The correct dosage of diphenhydramine for dogs depends on their weight. A small dog will need much less than a big dog to receive the same positive effects. According to the Merck Veterinary Manual, the safe dosage is 2-4 milligrams of medication per kilogram of weight, or 0.9 to 1.8 milligrams per pound. This amount can be administered two to three times daily, depending on your dog’s symptoms. 

While it’s best to use vet-approved Benadryl tablets or ointments, in some cases it is possible to use tablets intended for humans. If you choose to do this, keep these things in mind:

• First, never offer your dog medications with decongestants or alcohol in the formula. Only offer them medications with diphenhydramine and no other active ingredients. Decongestants and alcohol can be toxic for your dog. 
• Second, dogs should never be given time-released drug capsules. Your dog’s stomach works differently from yours, and a capsule that works well for humans may overdose your dog.  Plus, if they bite the capsule, they may get the entire dose at once instead of it being spread out over time. 
• Third, for small dogs, it may be better to use children’s Benadryl than Benadryl for adults. This lets you adjust the dose more carefully. 
• Finally, if you are going to use liquid Benadryl medication instead of tablets, talk to your dog’s vet to make sure you use the right dosage. Liquid medication is absorbed differently, and the 2-4 milligrams per kilogram guideline may not apply. 

Risks of Benadryl for dogs. While the right dose of Benadryl is safe for most dogs, occasionally a dog may be allergic to the medication itself. An allergy to diphenhydramine will have similar symptoms to other allergies, including:

• Red rashes on the skin
• Swelling of the face and tongue
• Diarrhea, vomiting, and upset stomach
• Skin chewing or licking

Almost all symptoms due to medication will be noticeable during the first hour after consuming the substance, so keep an eye on your dog for any changes in behavior. Dogs may also experience a number of more common, less dangerous side effects to Benadryl, like:

• Sleepiness
• Dry mouth
• Rapid breathing
• Hypersalivation
• Increased heart rate

These milder symptoms will fade as the medication leaves their system. 

Benadryl overdose. Ignoring any of these guidelines can lead to an overdose of diphenhydramine, with symptoms ranging from seizures to respiratory failure to a coma, depending on the size of the overdose. If you believe your dog has overdosed on Benadryl, contact your vet immediately and follow their instructions for emergency treatment.

Alternatives to Benadryl for dogs. If your dog reacts poorly to Benadryl but needs regular allergy treatment for a seasonal allergy, there are some alternatives you can use. Both cetirizine (Zyrtec) and loratadine (Claritin) are considered safe for dogs in the right dosage. However, they are also frequently combined with other ingredients like decongestants, which can hurt your dog. Always consult with a vet before giving your dog any new medication. 

For acute allergic reactions, it’s better to use faster-acting methods of reducing itching, such as cortisone creams or shots. These treatments begin to work in minutes. However, cortisone treatments are best for short-term use and may lead to uncomfortable side effects for your pet. 

When to call your vet. In an emergency, you should always call your vet first. Your dog may experience anaphylactic shock from their allergies, or in rare cases, from Benadryl itself. Call the vet immediately if your dog is: 

• Experiencing seizures
• Vomiting
• Experiencing diarrhea
• Swelling
• Struggling to breathe

These may be signs of a serious allergic response that needs immediate treatment. Similarly, if your dog has been bitten by a snake or stung by an unfamiliar insect, call your vet immediately to ensure your dog has not been poisoned. 

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How much baby Benadryl can be given to a dog?

Contents

Most diphenhydramine (Benadryl) tablets have a dose of 25mg, which would be an appropriate size for a 25lb dog. Smaller dogs will require you to cut or split these 25mg tablets. In this case, children’s Benadryl chewable tablets may be a good option. They are available in a dosage of 12.5 mg.

How much liquid Benadryl baby can I give my dog?

Benadryl dosage

	Maximum dose (every 8-12 hours)	Maximum dose (every 8-12 hours)
Dog weight	Tablet (mg)	Baby liquid (ml)
1 lb – 10 lb	1 mg – 10 mg	0. 4 ml – 4 ml
10 lb – 20 lb	10 mg – 20 mg	4 ml – 8 ml
20 lb – 30 lb	20 mg – 30 mg	8 ml – 12 ml

Can I give my dog ​​Benadryl Liquid Baby?

Benadryl Liquid for Children can be used in small dogs at the same dosage. Avoid Adult Liquid Benadryl Blend as it often contains alcohol, which is toxic to dogs. As with any flavored human medication, always test inactive ingredients for xylitol, a sweetener that is extremely toxic to dogs.

How much baby Benadryl can I give my 70-pound dog?

According to the Merck Veterinary Manual, the safe dosage is 2-4 milligrams per kilogram of body weight, or 0.9 to 1.8 milligrams per pound.

Which children’s Benadryl is safe for dogs?

Small dogs weighing less than 25 pounds can take Liquid Benadryl Children’s Formula. Liquid infant formula is easier to dose for small dogs than tablets. Stick to the children’s liquid Benadryl formula, as the adult version contains alcohol, which is toxic to dogs.

How many mg of Benadryl in 5 ml?

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How much baby Benadryl can I give my 15 pound dog?

How many mg of Benadryl should I give my dog? The standard dose of Benadryl for dogs is one mg per pound, or 2.2 mg per kilogram.

How many mg of Benadryl are in 10 ml?

Benadryl dosage chart

Weight	Benadryl liquid 5 ml = 12.5 mg	Benadryl chewable 1 tablet = 12. 5 mg
33-43 lbs	5 ml (12.5 mg)	1 tablet (12.5 mg)
44-54 lbs	7.5 ml (18.75 mg)	1.5 tablets (18.75 mg)
55-100 lbs	10 ml (25 mg)	2 tablets (25 mg)
100 pounds or more	20 ml (50 mg)	4 chewable (50 mg)

What can you give your dog for severe itching?

Benadryl is commonly used to treat itching in dogs caused by skin allergies and also reduces many other allergy symptoms, including: link to akc.org.

Is Benadryl Chewable for Children safe for dogs?

Most diphenhydramine (Benadryl) tablets have a dose of 25mg, which would be an appropriate size for a 25lb dog. Smaller dogs will require you to cut or split these 25mg tablets. In this case, children’s Benadryl chewable tablets may be a good option. They are available in a dosage of 12.5 mg.

How long does it take for Benadryl to start working in dogs?

Benadryl usually starts working after 30 minutes and you want your puppy to be calm and not anxious. As for the form of Benadryl, that is entirely up to your veterinarian. It doesn’t really matter if you use a brand name drug or not.

How long will Benadryl make my dog ​​sleep?

Dr. Selmer: In dogs, Benadryl usually lasts 8-12 hours.

Can dogs have human Benadryl?

Benadryl is safe to give to your dog for allergies, anxiety, motion sickness and vaccine side effects. Although a typical Benadryl tablet is 25 mg, you should only give your dog 0.9-1.8 mg per pound of weight. Make sure the Benadryl you give your dog only contains diphenhydramine.

Can a dog overdose with Benadryl?

Can dogs overdose on Benadryl? Yes, a dog can ingest or receive a dangerous dose of Benadryl. Fortunately, when treated promptly by a veterinarian, Benadryl toxicity usually produces excellent results in healthy animals.

12.5 mg equals 5 ml?

Dosage: every 4 hours. We recommend 12.5 mg. per 5 ml of strength.
Benadri 12.5 mg. per 5 ml (Dimedrol)

How many milligrams are in 5 ml?

How many milligrams are in a milliliter?

Volume in milliliters:	Weight in milligrams:
	water	Granulated sugar
5 ml	5,000 mg	4.227 mg
6 ml	6,000 mg	5. 072 mg
7 ml	7,000 mg	5.917 mg

How much Benadryl can a 5 pound dog have?

The calculation for Benadryl is pretty simple, just 1mg per pound, so for a 5lb dog it would be about 5mg. Because Benadryl comes in 25mg dosages, this is usually close to 1/4 tablet and there is a wide margin of safety for Benadryl so 1mg or 2mg above or below is well tolerated. Expect some drowsiness, like humans.

Is baby Benadryl xylitol?

Benadryl Infant Liquid Formula does not contain alcohol or xylitol. Below are some of the dog-safe active ingredients you can find in Benadryl products.

Is Benadryl for children the same as Benadryl for children?

Benadryl is a medicine used to relieve allergy symptoms, including sneezing, itching, and skin rashes. Benadryl is available in several forms, some of which contain doses suitable for children aged 6 years and older.
Benadryl dosage for infants.

How many mg per ml of liquid?

Therefore, there should be 1,000 milligrams in a milliliter, so the formula to convert mg to ml is: ml = mg/1000.

How many fluid milligrams are in a teaspoon?

How many milligrams are in a teaspoon?

What is the best allergy medicine for dogs?

The best allergy medicine for dogs is Apoquel tablets for dogs. This drug treats the most common form of allergy in dogs, skin irritation, quickly and with little or no side effects.

Why does my dog ​​itch so much, but doesn’t have fleas?

If your dog is still itching but doesn’t have fleas or food allergies, he may be allergic to things like pollen or dander. Changing diet may not make much of a difference, but your veterinarian may recommend a therapeutic diet to improve your dog’s skin health.

Why does my dog ​​constantly scratch and bite?

Among the most common causes of a dog’s compulsive licking, chewing, or scratching behavior are fleas, ticks, and ticks. While mites are often visible to the naked eye, fleas often go unnoticed until a large infestation develops and the mites become microscopic.

What helps to quickly get rid of itching?

To soothe itchy skin, dermatologists recommend the following tips:

1. Apply a cold damp cloth or ice pack to itchy skin.
2. Take an oatmeal bath.
3. Moisturize your skin.
4. Use local anesthetics containing pramoxine.
5. Use coolants such as menthol or calamine.

Is Benadryl grape flavor safe for dogs?

If your pet eats a grape-flavored product (which is found in some grape-flavored pet products and synthetic medicines), don’t worry, it’s not toxic. Most products are made from diluted grapes, but this is not enough to cause concern.

Will Benadryl calm the dog?

You may have heard that Benadryl can be used as a sedative to calm your dog while travelling, during fireworks or thunderstorms. It is true that Benadryl can relieve symptoms in some dogs, but the sedative effects are mild and not as pronounced in dogs as they are in humans.

Does Benadryl make dogs breathe faster?

Some dogs actually have the opposite reaction to Benadryl and become more hyperactive than sedative. Other side effects include dry mouth, increased heart rate, trouble urinating, and even rapid breathing.

How to calm a dog with Benadryl?

Try Benadryl if your dog also suffers from allergies.

If your veterinarian says this is normal, give your dog 2 mg of Benadryl per 1 kg (2.2 lb) of body weight, or follow your veterinarian’s dosage recommendations. Repeat dose every 4-6 hours until you need to calm the dog.

What is the difference between canine Benadryl and human Benadryl?

Summary. Benadryl (dipenhydramine), over-the-counter for humans, is the same medicine that is used in animals with the advice and supervision of a veterinarian.

How many ml in 160 mg?

Milligram to Milliliter Conversion table

Weight in milligrams:	Volume in milliliters:
	water	Granulated sugar
150 mg	0.15 ml	0. 177441 ml
160 mg	0.16 ml	0.189271 ml
170 mg	0.17 ml	0.2011 ml

0.5 mg less than 1 mg?

Answer. Hello Tracey. Yes. 5mg of lorazepam (generic name for Ativan) is less than 1mg, that’s half a mg.

What does mg/ml mean?

Milligrams (mg) measures weight and milliliters (ml) measures volume of liquid. Part of the word “milli” comes from the Latin word for “thousand”. There are 1,000 milligrams in a gram and 1,000 milliliters in a liter of liquid.

5 mg is equal to a teaspoon?

The milligram unit is most commonly used in medicine and pharmacies. Teaspoon: A unit of medicine or dose, equal to 5 milliliters. The unit is abbreviated tsp. Converting milligrams (mg) to teaspoons (tsp): 1 mg is approximately equal to 0.0002 teaspoons.

How many ml in 60 mg?

Solution: Convert milligrams to milliliters, 1 milligram equals 0. 001 milliliters, 60 milligrams equals 0.06 milliliters.

How many teaspoons are in 5 mg?

A teaspoon is a unit of volume equal to one third of a tablespoon. One teaspoon equals approximately 4.9 milliliters, but in food labeling, one teaspoon equals exactly 5 milliliters.

Can Benadryl be cut in half?

Also, do not split extended release tablets unless they have a score line and your doctor or pharmacist has told you to do so. Swallow the whole or divided tablet without crushing or chewing. If you are taking chewable tablets, chew each tablet thoroughly before swallowing.

How much Benadryl do I give for £32?

Diphenhydramine (Benadryl) Dosage Chart

Diphenhydramine (Benadryl) Dosage (ANTIHISTAMINE)
Weight	Liquid 12.5mg/5ml (teaspoon)	Chewable 12.5 mg
17-21 kg	¾ teaspoon = 3.75 ml	Use fluid
22-32 kg	1 teaspoon = 5 ml	1 Chew
33-42 kg	1 ½ tsp = 7. 5 ml	1 ½ chewable tablets

Is Benadryl dosage based on weight?

Benadryl dosage is based on weight, not age. The following table can help determine the correct dose for your child based on your child’s weight, but it does not replace the advice of your doctor and you should always call your pediatrician if you have any questions.

What does 20 mg/ml mean?

Updated May 02, 2018 By Claire Gillespie. Milligrams per milliliter (mg/mL) is a measure of the concentration of a solution. In other words, it is the amount of one substance dissolved in a certain volume of liquid. For example, a 7.5 mg/ml salt water solution contains 7.5 milligrams of salt for every milliliter of water…

How do you convert ml to mg?

Milliliter to Milligram formula:

Converting milliliter to milligram is very easy. Since 1 milligram is equal to 0.001 milliliter, this can be written as 1 mg = 1/1000 ml. Based on this equation, 1/1000 ml = 1 mg, so 1 ml = 1000 mg.