RN, BA, MA, MSN
If you are under thirty, you may have never heard of Mercurochrome.
Mercurochrome acts as a disinfectant, stopping bacteria from reproducing and spreading. When I was a child, the aqueous solution, used to prevent infection from minor scrapes and cuts, painted the lower extremities of 1970s youth with a distinct red color.
Despite its widespread use, Mercurochrome had two problems. Being red, it became difficult to detect inflammation around a wound. And Mercury, the active ingredient in Mercurochrome, is toxic to the human body.
Wander into any bathroom, and above the sink you will find a cabinet. Most often behind these cabinets you will find toothpaste, cotton swabs, cough drops, nail clippers, a pair of tweezers, and a handful of over-the-counter (OTC) medications for coughs and headaches whose use can be so widespread, they become ubiquitous. For example, diphenhydramine, more popularly known as Benadryl, for urticaria and allergic reactions.
Being ubiquitous does not imply safety. It is time we examine diphenhydramine overuse after seventy-five years in the medicine cabinet next to the Mercurochrome.
In 1946, the Food and Drug Administration (FDA) approved Benadryl® for prescription use. By 1985, it reached over-the-counter status.
For decades, consumers and medical professions alike used diphenhydramine as a sleep aid, urticaria treatment and as a drug in the protocol of allergic reactions. The mention of hives and Benadryl are near synonymous within our vernacular.
Today, for every case of diphenhydramine overuse, better options with better outcomes exist. The FDA approval odds of Benadryl® in today’s marketplace are slim. Antihistamines are problematic. They cross the blood-brain barrier, causing sedation and sleepiness that can persist after a nighttime dose into the following day.
This hangover effort lingers in the central nervous system (CNS) long beyond its therapeutic action, causing profound impairment that can slow reflexes. As a classification, antihistamines impair cognition, psychomotor and perception functions without subjective sleepiness.
Benadryl® is not selective in binding to the H1 receptor. Leaving patients with more of an anticholinergic response, which can lead to urinary retention, constipation, and elevated temperature.
Diphenhydramine is one of the most commonly abused medications. Most intoxication / overdose cases occur in children ages 6 years or younger.
In the wake of the Benadryl challenge that has resulted in seizures, coma, and death, careful storage of diphenhydramine and other OTC and prescription medicines becomes paramount.
Dose-induced hallucinations and overdoses need sedation to combat secondary agitation. In opposition to Benadryl, second and third generation H1 blockers have an improved risk profile and similar benefits.
Medications such as Zyrtec and Allegra do not cross the blood-brain barriers as easily. Causing less sedation and less cognitive impairment with equivalent symptom relief.
In emergency nursing and emergency medical services, we administered diphenhydramine for severe urticaria and hives. In fact, EMS allergic/anaphylaxis management protocols include an H1 antihistamine, either IM or IV.
Yet for decades research has recommended against antihistamines during the acute phase of an allergic reaction with no evidence from randomized controlled trials to support H1‐antihistamines in the emergency management of anaphylaxis.
Epinephrine is the drug of choice for anaphylaxis with adjunct symptom control through second and third generation drugs, including Levocetirizine (Xyzal), Loratadine (Claritin), Desloratadine (Clarinex) Cetirizine (Zyrtec) and Fexofenadine (Allegra).
Diphenhydramine has the benefits of IM, IV, and PO administration. Best use case is symptom control after stabilization. With urticaria, second and third generation drugs, medical providers can increase the dose up to (4x daily dose) before adding steroids.
As a sleep aid, diphenhydramine does not generate good sleep, though is helpful in inducing sleep and causing drowsiness. It increases the time to REM sleep and reduces sleep quality, and the risks and hangover tradeoffs far outweigh the drug’s benefits.
Because Benadryl® is so ingrained in our medical lexicon, its use continues amongst the lay population contributes to diphenhydramine overuse for children. But newer medications are safer, especially in children. In Canada, Benadryl® was the most recommended antihistamine in children.
The next time you reach into the medicine cabinet to treat a case of hives, consider cimetidine (Tagamet) or famotidine (Pepcid) as a better, safer alternative. And to treat childhood allergies, the second-generation antihistamines (Claritin®, Zyrtec®, and Allegra®) have a longer duration (18-24 hours) when compared with Benadryl® (4-6 hours) with fewer side effects.
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