What are the potential harms of Benadryl (diphenhydramine) to patients?

From the Guidelines

Benadryl (diphenhydramine) can be harmful to patients due to its potential to cause sedation, performance impairment, and anticholinergic effects, which can be particularly problematic in vulnerable populations such as the elderly and children under 6 years. The use of Benadryl can lead to drowsiness, dizziness, dry mouth, blurred vision, constipation, and urinary retention, which can significantly impair daily activities and increase the risk of accidents and injuries 1. Additionally, the sedative effects of Benadryl can worsen cognitive function in elderly patients with dementia and increase the risk of falls and fractures.

The anticholinergic effects of Benadryl can also be problematic, particularly in older adults who are more sensitive to these effects and may experience increased risk of complications such as fractures and subdural hematomas caused by falls 1. Furthermore, the use of Benadryl in children under 6 years is generally not recommended due to the risk of paradoxical excitation and overdose sensitivity, and the potential for serious toxicity including seizures, heart rhythm disturbances, and hallucinations 1.

Some of the key potential harms of Benadryl include:

• Sedation and performance impairment, which can increase the risk of accidents and injuries
• Anticholinergic effects, such as dry mouth, constipation, and urinary retention
• Increased risk of falls and fractures in elderly patients
• Worsening of cognitive function in patients with dementia
• Risk of paradoxical excitation and overdose sensitivity in children under 6 years
• Potential for serious toxicity, including seizures, heart rhythm disturbances, and hallucinations, particularly when exceeding the maximum daily dose of 300mg.

It is essential to use Benadryl with caution and only under the guidance of a healthcare provider, particularly in vulnerable populations, and to carefully monitor for potential side effects and adverse reactions 1.

From the FDA Drug Label

Warnings Do not use • to make a child sleepy • with any other product containing diphenhydramine, even one used on skin Ask a doctor before use if you have • a breathing problem such as chronic bronchitis • glaucoma • trouble urinating due to enlarged prostate gland Ask a doctor or pharmacist before use if you are taking sedatives or tranquilizers When using this product • marked drowsiness may occur • avoid alcoholic drinks • alcohol, sedatives, and traquilizers may increase drowsiness • be careful when driving a motor vehicle or operating machinery • excitability may occur, especially in children If pregnant or breast-feeding, ask a healthcare professional before use Keep out of reach of children. In case of accidental overdose, get medical help or contact a Poison Control Center right away (1-800-222-1222)

The potential harms of Benadryl (diphenhydramine) to patients include:

• Marked drowsiness that may occur when using the product
• Increased risk of drowsiness when combined with alcohol, sedatives, and tranquilizers
• Excitability, especially in children
• Potential worsening of underlying medical conditions, such as:

• Breathing problems (e.g., chronic bronchitis)
• Glaucoma
• Urination problems due to an enlarged prostate gland

• Accidental overdose, which can be serious and requires immediate medical attention 2

From the Research

Potential Harms of Benadryl (Diphenhydramine)

The potential harms of Benadryl (diphenhydramine) to patients include:

• Overdose and toxicity, which can be severe and potentially fatal, as seen in a case report of a 14-year-old girl who ingested an unknown amount of diphenhydramine while taking part in a social media challenge 3
• Central nervous system depression, as reported in a case of a 13-year-old girl who presented with diphenhydramine intoxication and a false positive result for tricyclic antidepressants 4
• Cardiovascular effects, such as acute but transient ST segment elevation and echocardiographic evidence of severe pulmonary hypertension, as seen in a pediatric patient who self-injected crushed diphenhydramine capsules into her central venous catheter 5
• Cognitive decline and other adverse effects, including delirium, inattention, disorganized speech, and altered consciousness, particularly in older hospitalized patients 6
• Increased risk of urinary catheter placement and longer hospital stays, also seen in older hospitalized patients 6

Age-Related Differences in Diphenhydramine Effects

There are age-related differences in the effects of diphenhydramine, with:

• Elderly adults having a longer serum elimination half-life and lower clearance rates compared to young adults and children 7
• Children having a shorter serum elimination half-life and higher clearance rates compared to elderly adults and young adults 7
• Teenagers being a particularly susceptible group to the risks associated with diphenhydramine misuse, as seen in the case of the "Benadryl challenge" on social media 3

Important Considerations for Healthcare Providers

Healthcare providers should be aware of the potential harms of Benadryl (diphenhydramine) and:

• Monitor patients closely for signs of overdose and toxicity, particularly in vulnerable populations such as the elderly and children 3, 4
• Consider the possibility of cross-reactivity with other medications, such as tricyclic antidepressants, in patients with unknown acute drug intoxication 4
• Review the use of diphenhydramine carefully in older hospitalized patients, due to the increased risk of cognitive decline and other adverse effects 6