Diphenhydramine 50mg Capsules

Diphenhydramine is a first-generation antihistamine that competitively blocks H1 histamine receptors, preventing histamine from binding and exerting its effects (e.g., vasodilation, increased capillary permeability, pruritus). It readily crosses the blood-brain barrier, leading to significant central nervous system (CNS) effects, including sedation. It also possesses significant anticholinergic (muscarinic receptor blockade) effects, contributing to its antiemetic and antitussive properties, as well as common side effects like dry mouth and urinary retention.

Urgent Side Effects: Seek Medical Help Right Away

While rare, some people may experience severe and potentially life-threatening side effects when taking this medication. If you notice any of the following symptoms, contact your doctor or seek immediate medical attention:

Signs of an allergic reaction, such as:
+ Rash
+ Hives
+ Itching
+ Red, swollen, blistered, or peeling skin with or without fever
+ Wheezing
+ Tightness in the chest or throat
+ Trouble breathing, swallowing, or talking
+ Unusual hoarseness
+ Swelling of the mouth, face, lips, tongue, or throat
Severe dizziness or fainting
Changes in balance
Feeling less alert than usual

Other Possible Side Effects

Like all medications, this drug can cause side effects. Although many people may not experience any side effects or only have mild ones, it's essential to discuss any concerns with your doctor. If you experience any of the following side effects or any other unusual symptoms that bother you or do not go away, contact your doctor or seek medical help:

Dizziness or drowsiness
Thickening of mucus in the nose or throat
Feeling nervous or excitable
Upset stomach or vomiting

Reporting Side Effects

This list is not exhaustive, and you may experience other side effects not mentioned here. If you have questions or concerns about side effects, consult your doctor. You can also report side effects to the FDA at 1-800-332-1088 or online at https://www.fda.gov/medwatch. Your doctor can provide medical advice and guidance on managing side effects.

Before Taking This Medication: Important Information to Share with Your Doctor

It is essential to inform your doctor about the following:

Any allergies you have, including allergies to this medication, its components, or other substances, such as foods or drugs. Be sure to describe the symptoms you experienced.
If you are breastfeeding or plan to breastfeed, as you may need to avoid breastfeeding while taking this medication.
If the patient is a premature baby or newborn, as this form of the medication should not be administered to these individuals.

This medication may interact with other medications or health conditions. Therefore, it is crucial to provide your doctor and pharmacist with a comprehensive list of:

All prescription and over-the-counter medications you are taking
Any natural products or vitamins you are using
Your existing health problems

Before starting, stopping, or changing the dose of any medication, including this one, consult with your doctor to ensure your safety. It is vital to verify that it is safe to take this medication with all your other medications and health conditions.

It is essential to inform all your healthcare providers, including doctors, nurses, pharmacists, and dentists, that you are taking this medication.

To minimize the risk of severe side effects, adhere strictly to the dosage instructions provided by your doctor. Do not exceed the recommended dose, as this may increase your chance of experiencing severe side effects. Additionally, do not take this medication for a longer duration than prescribed by your doctor.

Until you are familiar with how this medication affects you, avoid operating a vehicle or engaging in any activities that require alertness.

Do not use this medication in conjunction with other products containing diphenhydramine. It is also recommended to avoid consuming alcohol while taking this drug.

Before using marijuana, other forms of cannabis, or any prescription or over-the-counter medications that may cause drowsiness, consult with your doctor.

Note that different brands of this medication may be suitable for children of various ages. Therefore, it is crucial to consult with a doctor before administering this medication to a child. Furthermore, do not use this medication as a means to induce sleep in a child; instead, discuss appropriate alternatives with your doctor.

If you are 60 years or older, exercise caution when using this medication, as you may be more susceptible to side effects. Similarly, when administering this medication to a child, use it with caution, as children may have a higher risk of experiencing excitability.

If you are pregnant or planning to become pregnant, inform your doctor, as it is necessary to discuss the potential benefits and risks associated with using this medication during pregnancy.

• Monoamine Oxidase Inhibitors (MAOIs) (concurrent use or within 14 days of MAOI discontinuation) - may prolong and intensify anticholinergic effects.

• CNS Depressants (e.g., alcohol, opioids, benzodiazepines, barbiturates, other sedatives, hypnotics, anxiolytics, tricyclic antidepressants, antipsychotics) - additive CNS depression, increased risk of profound sedation, respiratory depression, coma.
• Other Anticholinergic Drugs (e.g., atropine, scopolamine, tricyclic antidepressants, some antipsychotics, antispasmodics) - additive anticholinergic effects (e.g., dry mouth, blurred vision, urinary retention, constipation, confusion, delirium).

• Potassium Chloride (oral) - increased risk of gastrointestinal lesions due to decreased gastrointestinal motility.
• Beta-2 Agonists (e.g., albuterol) - theoretical increased risk of cardiac effects with high doses of both.
• Cholinesterase Inhibitors (e.g., donepezil) - anticholinergic effects of diphenhydramine may antagonize the therapeutic effects of cholinesterase inhibitors.

• Not typically categorized as minor; interactions are generally significant due to additive effects.

• Drowsiness
• Dizziness
• Dry mouth
• Blurred vision
• Urinary retention
• Constipation
• Nausea
• Vomiting
• Nervousness
• Paradoxical excitation (especially in children)
• Confusion (especially in elderly)

Generally considered Category B. Studies in animals have not shown risk, and human data suggest no increased risk of major birth defects. However, use during late pregnancy may cause irritability or tremors in the neonate. Use only if clearly needed and potential benefits outweigh risks.

Excreted into breast milk. Can cause sedation in the infant and may decrease milk supply due to its anticholinergic effects. Use with caution, monitor infant for drowsiness or irritability. Consider alternative antihistamines if possible, especially in newborns or premature infants.

Not recommended for children under 2 years of age for cough/cold symptoms due to risk of serious side effects including respiratory depression and paradoxical excitation. Use with caution in older children, as paradoxical excitation (restlessness, insomnia, nervousness) can occur. Dosing must be weight-based and accurate.

Increased susceptibility to adverse effects, particularly sedation, confusion, dizziness, and anticholinergic effects (e.g., dry mouth, urinary retention, constipation, blurred vision, falls). Included in the Beers Criteria as a medication to avoid in older adults due to high anticholinergic burden and risk of cognitive impairment and falls. Use lowest effective dose and for shortest duration possible.

• Diphenhydramine is a common over-the-counter medication, but its sedative and anticholinergic effects can be significant, especially in vulnerable populations like the elderly.
• Often misused as a primary sleep aid; long-term use is not recommended due to tolerance to sedative effects and increased anticholinergic burden.
• Patients should be advised about the potential for next-day sedation ('hangover effect') when used for sleep.
• Educate patients on the various brand names and combination products containing diphenhydramine to avoid accidental overdose or additive effects.
• Consider second-generation antihistamines (e.g., loratadine, cetirizine, fexofenadine) for allergy relief when sedation is undesirable.

• For allergies: Second-generation antihistamines (e.g., loratadine, cetirizine, fexofenadine), nasal corticosteroids, mast cell stabilizers (e.g., cromolyn)
• For insomnia: Non-pharmacologic sleep hygiene, melatonin, zolpidem, eszopiclone (prescription hypnotics)
• For motion sickness: Scopolamine (prescription patch), meclizine
• For cough: Dextromethorphan, guaifenesin (expectorant)

If your symptoms or health issues persist or worsen, it's essential to contact your doctor for further guidance. To ensure your safety, never share your medication with others or take someone else's medication. Some medications may come with an additional patient information leaflet, so be sure to check with your pharmacist for more information. If you have any questions or concerns about this medication, don't hesitate to reach out to your doctor, nurse, pharmacist, or other healthcare provider. In the event of a suspected overdose, immediately call your local poison control center or seek medical attention. When seeking help, be prepared to provide details about the overdose, including the medication taken, the amount, and the time it occurred.