Diphenhydramine: Uses, Dosage, Side Effects & Interactions Guide

Summary of Key Points

Diphenhydramine is an antihistamine commonly used to relieve symptoms of allergies, hay fever, the common cold, and conditions like insomnia and motion sickness. It works by blocking histamine, a substance in the body that triggers allergic reactions. Available over-the-counter in various forms, it’s important to follow dosing instructions carefully. Always consult a healthcare provider before making any changes to your medication regimen.

Names of Medication

US Brand Names: Benadryl, Banophen, ZzzQuil

Generic Name: Diphenhydramine

The generic name refers to the active ingredient in the medication, which is listed in parentheses next to the brand name.

Pharmacologic Category

Diphenhydramine belongs to several pharmacologic categories, including:

1. Antihistamines (First Generation)
2. Antiemetics
3. Antitussives
4. Hypnotics

Diphenhydramine Dosage

Diphenhydramine is used to treat a variety of conditions. Below are the recommended doses for adults. Always consult your doctor or one of our telemedicine providers before adjusting your dose.

Allergic Rhinitis (Hay Fever)

Adults: 25-50 mg by mouth every 4-6 hours as needed. Do not exceed 300 mg per day.

Allergic Conjunctivitis (Eye Allergies)

Adults: 25-50 mg by mouth every 4-6 hours as needed. Do not exceed 300 mg per day.

Urticaria (Hives)

Adults: 25-50 mg by mouth every 4-6 hours as needed. Do not exceed 300 mg per day.

Insomnia

Adults: 50 mg by mouth at bedtime. This should only be used for short-term treatment (no more than 2 weeks).

Motion Sickness

Adults: 25-50 mg by mouth 30 minutes before travel, then every 4-6 hours as needed. Do not exceed 300 mg per day.

Common Cold

Adults: 25-50 mg by mouth every 4-6 hours as needed for symptom relief. Do not exceed 300 mg per day.

Anaphylaxis (as adjunct treatment)

Adults: 25-50 mg by mouth every 4-6 hours as needed, in addition to epinephrine. Consult your doctor for specific instructions.

Insect Bites and Rashes

Adults: 25-50 mg by mouth every 4-6 hours as needed. Topical forms may also be applied to the affected area up to 4 times daily.

Dosage Forms and Strengths

Diphenhydramine is available in various forms and strengths, including:

1. Tablets: 25 mg, 50 mg
2. Capsules: 25 mg, 50 mg
3. Liquid: 12.5 mg/5 mL
4. Chewable Tablets: 12.5 mg
5. Topical Cream: 1%, 2%
6. Injectable Solution: 50 mg/mL

Administration Instructions

Diphenhydramine can be taken with or without food. If it causes stomach discomfort, try taking it with food or milk. For liquid forms, use a proper measuring device to ensure the correct dose. When using the topical form, apply a thin layer to the affected area and wash your hands afterward. Avoid contact with your eyes, nose, and mouth.

Diphenhydramine Side Effects

Like all medications, diphenhydramine can cause side effects, ranging from mild to severe. If you experience any serious reactions, contact a healthcare provider immediately.

1. Drowsiness: The most common side effect. Avoid driving or operating heavy machinery until you know how diphenhydramine affects you.
2. Dizziness: You may feel lightheaded or unsteady.
3. Dry Mouth: Diphenhydramine can reduce saliva production, leading to a dry mouth.
4. Blurred Vision: Some patients may experience difficulty focusing or blurred vision.
5. Constipation: This medication may slow down bowel movements.
6. Urinary Retention: Difficulty urinating can occur, especially in older adults.
7. Confusion: In some cases, particularly in elderly patients, diphenhydramine can cause confusion or memory problems.

Contraindications

A contraindication is a specific situation or condition where a medication should not be used because it may cause harm. It’s important to be aware of contraindications to avoid potential side effects or complications.

Here are the main contraindications for taking diphenhydramine:

1. Allergy to Diphenhydramine: If you’ve had an allergic reaction to diphenhydramine in the past, you should not take it again. Allergic reactions may include rash, itching, swelling, or difficulty breathing.
2. Glaucoma: Diphenhydramine can increase eye pressure, worsening glaucoma, a condition that damages the optic nerve.
3. Asthma or COPD: Diphenhydramine can thicken mucus and make breathing more difficult, potentially worsening asthma or chronic obstructive pulmonary disease (COPD).
4. Bladder obstruction or difficulty urinating: Diphenhydramine can cause urinary retention, complicating bladder issues.
5. Heart disease or high blood pressure: Diphenhydramine can increase heart rate and blood pressure, which may be dangerous for those with heart conditions.

Always consult with a healthcare provider before starting any new medication, especially if you have any of the conditions listed above. Our telemedicine providers are available to help you determine if diphenhydramine is safe for you.

Diphenhydramine Drug Interactions

Diphenhydramine can interact with other medications, increasing the risk of side effects or reducing the effectiveness of either drug. Here are some medications that may interact with diphenhydramine:

1. Alcohol: Combining alcohol with diphenhydramine can increase drowsiness and impair your ability to think clearly.
2. Sedatives or tranquilizers: Medications like lorazepam (Ativan) or alprazolam (Xanax) can enhance the sedative effects of diphenhydramine, leading to excessive drowsiness or dizziness.
3. Antidepressants: Medications such as amitriptyline (Elavil) or fluoxetine (Prozac) can increase side effects like dry mouth, blurred vision, and confusion when taken with diphenhydramine.
4. MAO inhibitors: Medications like phenelzine (Nardil) or selegiline (Eldepryl) can increase the risk of serious side effects when combined with diphenhydramine. These medications should not be taken together.
5. Other antihistamines: Taking multiple antihistamines, such as cetirizine (Zyrtec) or loratadine (Claritin), can increase the risk of side effects like drowsiness, dry mouth, and confusion.

Always inform your healthcare provider about all the medications you are taking, including over-the-counter drugs and supplements. Our telemedicine providers can help you review your medications and ensure there are no harmful interactions.

Diphenhydramine in Pregnancy

Is it safe to take Diphenhydramine during pregnancy? The FDA classifies Diphenhydramine as a Category B medication for pregnancy. This means that animal studies have not shown harm to the fetus, but there are no well-controlled studies in pregnant women. While it is generally considered safe for short-term use, it’s crucial to consult your healthcare provider before taking Diphenhydramine during pregnancy. They can help you weigh the potential benefits and risks based on your individual circumstances.

Diphenhydramine While Breastfeeding

Is it safe to take Diphenhydramine while breastfeeding? Diphenhydramine can pass into breast milk and may affect a nursing infant. It can cause drowsiness, irritability, or even reduce milk production in some women. If you are breastfeeding, it’s important to consult your healthcare provider before using Diphenhydramine. They can help you determine whether the benefits outweigh the potential risks for both you and your baby.

Estimated Cost of Diphenhydramine

The estimated cost of a 30-day supply of Diphenhydramine (25 mg tablets, taken as directed) without insurance is approximately $5 to $10 when using a GoodRX coupon. Prices may vary depending on the pharmacy and location, so it’s a good idea to compare prices using online tools like GoodRX to find the best deal.

Possible Alternatives to Diphenhydramine

If Diphenhydramine is not suitable for you, there are alternative treatments and lifestyle changes that may help manage your symptoms. Always discuss these options with your healthcare provider before making any changes to your treatment plan. Our telemedicine providers are available to help you explore these alternatives.

Alternatives for Allergic Rhinitis (Hay Fever)

Non-sedating antihistamines such as loratadine (Claritin) or cetirizine (Zyrtec), nasal corticosteroids like fluticasone (Flonase), and saline nasal sprays are common alternatives. Lifestyle changes, such as avoiding allergens and using air purifiers, may also provide relief.

Alternatives for Allergic Conjunctivitis

Eye drops containing antihistamines like ketotifen (Zaditor) or mast cell stabilizers such as olopatadine (Pataday) can be effective. Additionally, avoiding allergens and applying cold compresses may help alleviate symptoms.

Alternatives for Urticaria (Hives)

Non-sedating antihistamines like fexofenadine (Allegra) or cetirizine (Zyrtec) are often recommended. In more severe cases, corticosteroids may be prescribed. Identifying and avoiding known triggers is also essential in managing hives.

Alternatives for Insomnia

Non-habit-forming sleep aids like melatonin, along with lifestyle changes such as improving sleep hygiene (e.g., establishing a consistent sleep schedule, reducing screen time before bed), may be beneficial for managing insomnia.

Alternatives for Motion Sickness

Medications like meclizine (Antivert) or scopolamine patches are commonly used alternatives. Behavioral techniques, such as focusing on the horizon or sitting in the front seat of a vehicle, can also help reduce symptoms.

Alternatives for Common Cold

Decongestants like pseudoephedrine (Sudafed) or saline nasal sprays may help relieve cold symptoms. Additionally, rest, staying hydrated, and using a humidifier can support recovery.

Alternatives for Anaphylaxis (as Adjunct)

Epinephrine (EpiPen) is the first-line treatment for anaphylaxis. While Diphenhydramine may be used as an adjunct, it is not a substitute for epinephrine. If you are at risk for anaphylaxis, always carry an epinephrine auto-injector and use it as directed in an emergency.

Alternatives for Insect Bites and Rashes

Topical corticosteroids like hydrocortisone cream or oral antihistamines such as loratadine (Claritin) may help reduce itching and swelling. Applying cold compresses and avoiding scratching can also provide relief.

Recent Updates on Diphenhydramine Research

Recent research has focused on the potential long-term effects of Diphenhydramine, particularly in older adults. Studies suggest that prolonged use of anticholinergic medications like Diphenhydramine may increase the risk of cognitive decline and dementia in older adults. As a result, healthcare providers are becoming more cautious about recommending Diphenhydramine for long-term use, especially in elderly patients.

Additionally, ongoing studies are exploring the use of Diphenhydramine in combination with other medications for treating severe allergic reactions and anaphylaxis. While Diphenhydramine remains a common adjunct treatment, researchers are investigating whether other medications may offer more effective or safer alternatives.

As always, consult your healthcare provider before making any changes to your medication regimen. Our telemedicine providers are available to discuss the latest research and help you make informed decisions about your health.

James Kingsley

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