Benadryl (Diphenhydramine) is an over the counter (OTC) medication used to treat cold or allergy symptoms such as sneezing, runny nose, watery eyes, hives, skin rash, itching, etc. Benadryl can also be used to treat motion sickness, to induce sleep, and to treat certain symptoms of Parkinson’s disease. Benadryl belongs to a class of medications called antihistamines, which works by reducing the effects of the natural chemical histamine in the body. It does this through its effects as an inverse agonist of histamine receptors in the body. This means that it attaches to histamine receptors at the same point that agonists (chemicals that increase the actions of other chemicals) typically bind to, and blocks both the histamine chemical itself as well as the actions of any agonists that may increase histamine levels. By reducing the effects of histamines on the capillaries (small blood vessels), Benadryl can reduce allergic symptoms. Its effects on the histamine receptors also cause drowsiness, allowing for it to be used for inducing sleep. For the treatment of Parkinson’s symptoms, Benadryl blocks the effects of muscarinic acetylcholine receptors in the brain, which can cause several Parkinson’s symptoms. Benadryl also works as a sodium channel blocker, allowing it to act as a local anaesthetic. Through this, Benadryl can reduce overstimulation of the inner ear, and reduce motion sickness.

Manufacturer Information

Canadian Pharmacy King currently offers the brand Benadryl from Canada by Johnson & Johnson. The generic Diphenhydramine comes from Canada by a different manufacturer. The brand Benadryl and the generic Diphenhydramine is available in several formats and strengths.

Brand Benadryl:

• Benadryl Itch Spray - 2 %/0.1 %/59 ml;
• Benadryl Itch Stick - 2 %/0.1 %/14 ml;
• Benadryl child liquid 100 mg & 250 ml - 6.25 mg/5 ml;
• Benadryl caplets and Liqui-Gels - 25 mg

Generic Diphenhydramine:

• Diphenhydramine Oral Elixir - 12.5 mg/5 ml;
• Diphenhydramine capsules - 25 mg;
• Diphenhydramine extra strength tablets - 50 mg;
• Diphenhydramine Injection Vial - 50 mg/ml

Common side effects of Benadryl may include dizziness, drowsiness, loss of coordination, dry mouth, nose, or throat, constipation, upset stomach, dry eyes, blurred vision, or daytime drowsiness or “hangover” feeling after nighttime use. Stop taking Benadryl and call your doctor immediately if you notice any of the more serious side effects such as:

• Confusion, feeling like you might pass out;
• Little or no urination;
• Painful or difficult urination;
• Pounding heartbeats or fluttering in your chest;
• Tightness in your neck or jaw, uncontrollable movements of your tongue

Older adults may be more likely to have side effects from this medication. If you notice any severe side effects or signs of an allergic reaction, seek emergency medical attention.

You should not use Benadryl if you are allergic to diphenhydramine. To make sure Benadryl is safe for you, tell your doctor if you have a blockage in your digestive tract, a bladder obstruction or other urination problems, a colostomy or ileostomy, liver or kidney disease, asthma, chronic obstructive pulmonary disease (COPD), heart disease, low blood pressure, emphysema, chronic bronchitis, glaucoma, a thyroid disorder, or if you take potassium supplements. Benadryl is not expected to harm an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant to ensure there are no complications. Benadryl can pass into breast milk and may harm a nursing baby, and it may slow breast milk production. Ask a doctor before using this medication if you are breastfeeding. This medication should not be given to a child younger than 2 years old.

Benadryl may cause blurred vision and may impair your thinking or reactions. Do not drive or operate heavy machinery until you know how this medication will affect you. Drinking alcohol may increase certain side effects of this medication, including dizziness and drowsiness. Limit alcohol consumption while using Benadryl. Benadryl may interact with several medications, especially sleeping pills, narcotic pain relievers, muscle relaxants, antidepressants, medications for anxiety, or medication for seizures, as well as other cold, cough, or allergy medications. This is not a complete list of interactions, and others may occur. Tell your doctor about any medications, vitamins, or herbal supplements you are currently taking or have recently taken in order to reduce the risk of any possible interactions.

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