Benadryl (Diphenhydramine)

What is Benadryl?

Benadryl (diphenhydramine) is an antihistamine drug which treats allergies and cold symptoms.

What is Benadryl used for?

Benadryl is used to relieve allergic symptoms as well as to treat hay fever and common cold. It can also be used in the prevention and treatment of symptoms of motion sickness such as nausea, vomiting and dizziness. However, this drug does not treat cough caused by asthma, emphysema or smoking.

How does Benadryl work?

The main component of Benadryl is diphenhydramine which acts as an anti-histamine agent. Histamine causes allergic symptoms such as sneezing, watery eyes, runny nose, itching etc. Diphenhydramine decreases levels of this naturally occurring chemical in the body and relieves such symptoms.

How to use Benadryl

Benadryl should be used in the manner prescribed by a doctor or as directed by your pharmacist. Taking the drug for longer period of time or in larger amount may prove to be extremely harmful. The dosage depends on your age, medical condition and response to treatment.

Benadryl is available in two forms: caplet and oral suspension.

Benadryl caplet or oral suspension may be taken with or without food. If you experience stomach upsets, you can take it with food or milk. If you are using the oral suspension shake the bottle well before use and measure the dose carefully with a dose-measuring device.

To prevent motion sickness, the medicine needs to be taken at least 30 minutes prior to the start of the journey.

Benadryl can alter results of allergy skin tests. Inform your doctor that you are taking this drug before undergoing such tests.

Do not increase or stop your dose without consulting your doctor. However, if your condition does not improve at all or becomes worse contact your doctor immediately.

Benadryl warnings and precautions

Benadryl is not administered to patients who are allergic to diphenhydramine. Patients who have taken a MAO inhibitor in the past two weeks are strictly prohibited from taking this drug.

Before taking this drug, inform your doctor about your medical conditions, especially if you are allergic to any other drug or if you have any of the following conditions: cough with phlegm, liver disease especially cirrhosis of liver, high blood pressure, heart disease, kidney disease, enlarged prostate, urination problems, diabetes, glaucoma, or a thyroid disorder.

You should be careful about the dose of Benadryl as an overdose can cause serious damage to your liver. Alcohol intake along with this drug may aggravate your liver damage.

Extreme caution should be maintained while administering this medicine to young children as misuse of such a drug can have fatal consequences in children.

Drink plenty of fluids while taking Benadryl.

Benadryl is considered to be harmful to a fetus. It is also believed to pass through breast milk. Therefore, pregnant and lactating women are advised to discuss the possible risks and benefits of taking the drug with their doctors.

What do I do if I have missed a Benadryl dose?

If you have missed a Benadryl dose, take it as soon as you remember. If, however, it is almost time for the next dose, the missed dose can be skipped. Do not take a double dose.

What do I do if I have taken a Benadryl overdose?

If you have taken an overdose of Benadryl, consult your doctor immediately.

Benadryl interactions

Before taking this drug, you should inform you doctor if you are taking any sleep-inducing medicine such as sleeping pills, sedatives, muscle relaxants, narcotic pain medicines, medicine for depression, anxiety or seizures, or other cough and cold medicine. These medicines may increase drowsiness caused by Benadryl. 

Other drugs which can also interact with Benadryl are: diuretics, beta-blockers, aspirin or other salicylates, medication for gout, blood pressure, irritable bowel, or bladder movements and urination problems; bronchodilators, antidepressants, zidovudine, or isoniazid.

Hence it is necessary to inform your doctor about all the prescription/non prescription drugs/herbal medicines that you are taking, before taking this drug.

You should not start taking any new medicine, without consulting your doctor.

Benadryl side effects

Side effects from Benadryl include allergic reactions such as swelling of tongue, face, throat, hives, redness of skin etc. as well as some serious symptoms such as severe dizziness, anxiety, restlessness, nervousness, hallucinations, confusion, unusual thoughts, increased blood pressure, decreased urination, loss of appetite, nausea, stomach pain, or jaundice.

Insomnia, dizziness, drowsiness, mild stomach pain, blurred vision, restlessness, excitement in children, dry mouth, problems with concentration or memory, redness, warmth or tingling sensation under skin are some less serious side effects of Benadryl.