Benadryl

Brand Name:Allerdryl, Allernix, Diphenhydramine Hydrochloride Injection USP, Nytol, Simply Sleep, Unisom Extra Strength, Unisom Extra Strength Sleepgels

Prescription needed: No

What is this drug used for?

Diphenhydramine belongs to a class of drugs called antihistamines and is primarily used to treat hives, seasonal allergies or allergic rhinitis, symptoms of the common cold and allergic reactions to drugs, food and/or insect stings.

It may also be used for short-term sleep problems, to prevent and treat symptoms of vertigo and motion sickness and to treat some movement disorders caused by some medications.

Is there any reason not to take this drug?

You should not take this drug if you are allergic to diphenhydramine or dimenhydrinate. Tell your doctor if you have or have ever had:

  • glaucoma (narrow-angle)
  • problems with your kidney or liver
  • problems with your prostate
  • any heart rhythm problems
  • asthma or other chronic lung diseases
  • difficulty going to the bathroom (urinary incontinence or urinary retention)
  • problems with constipation or blockage of intestines
  • an overactive thyroid gland (hyperthyroidism)

What about possible side effects?

The most common side effects are:

  • feeling drowsy
  • feeling dizzy
  • dry mouth, nose or throat
  • constipation

Other less common side effects include:

  • difficulty urinating
  • headache
  • blurry vision
  • feeling excited or hyper (may see this in children or elderly)
  • feeling confused or hallucinating
  • feeling off-balance or unsteady on your feet
  • irregular, fast heartbeat

This is not a complete list of side effects. If you are concerned about these or other unusual symptoms while taking this medication, ask your doctor and/or pharmacist for more information and advice.

What if I am taking other drugs?

Always provide your doctor with a list of all other drugs you are taking (including over-the-counter medications and herbal/natural products) as they may interact with and/or may change the safety or effectiveness of either drug. Tell your doctor specifically if you are taking any of these drugs as these are the most common interactions and he/she may need to make changes or monitor you more closely:

Drugs that can cause tiredness, sedation, dizziness or increase the chances of having the same side effects - talk to your doctor or pharmacist if you are taking any of the following drugs:

  • opioid pain medications (e.g. codeine, oxycodone, morphine, hydromorphone)
  • some antidepressants (e.g. sertraline, paroxetine, trazodone), medications for anxiety (e.g. lorazepam, diazepam) and antipsychotics (e.g. risperidone, haloperidol)
  • muscle relaxants (e.g. cyclobenzaprine)
  • drugs for epilepsy (gabapentin, pheytoin, phenobarbital, carbamazepine, valproic acid)
  • Drugs that have anticholinergic effects (e.g. amitriptyline, desipramine, imipramine; ask your doctor or pharmacist) - increase your chances of having similar side effects
  • Procarbazine, selegiline, tranylcypromine and other MAO-inhibitor drugs - may increase your chance for some side effects to diphenhydramine

This is not a complete list of drug interactions. Ask your doctor or pharmacist to review your list of medications.

Other information:

Special Instructions:

  • If you are planning on having any skin tests for allergies, tell your doctor that you are taking this medication as it may affect the results of your allergy test.
  • If using this medication for a long time, you may notice that it is not working as well since it tends to lose its effect over time. Talk to you doctor or pharmacist. This medication is usually intended for short-term use only

Children: Can be used but lower doses are necessary. Children may show signs of excitement and hyperactivity versus drowsiness. Talk to your doctor or pharmacist.

Seniors: Are more sensitive to side effects and lower doses are usually necessary, especially at the start of therapy. May see signs of excitement and agitation as opposed to drowsiness. Talk to your doctor or pharmacist.

Pregnancy: Has been used in pregnancy but should not be done without talking to your doctor or pharmacist first.

Women who are nursing: This drug passes into breast milk. May decrease milk production. Talk to your doctor.

People who drive or operate machinery: Should not do so until they know how this drug affects them personally. May cause drowsiness.

Alcohol: Avoid the use of alcohol as it may increase the sedating effects of diphenhydramine.

Overdose: A large overdose of this medicine could cause severe and unusual drowsiness. If you experience any unusual reactions or if you seriously exceed the recommended dosage, call your doctor or 911.

Stopping the drug: You can stop this medication whenever it is no longer needed. It is meant to be used on an as needed basis.

If you miss a dose: Take it when you remember. However, if your next dose is within two hours, don’t take the missed dose. Instead, wait and take the next scheduled dose. Do not take a double dose.

Storage conditions: Closed container; cool, dry location away from excess moisture (not in the bathroom) and light; always out of reach of children.

Dietary precautions: None