Benadryl is a widely recognized over-the-counter medication used for various symptoms. Understanding its proper dosage is important for safety and effectiveness, ensuring individuals experience intended benefits without encountering potential risks.
Understanding Diphenhydramine
The active ingredient in Benadryl is diphenhydramine hydrochloride, or diphenhydramine HCl. This substance belongs to a class of drugs known as first-generation antihistamines. Its primary function involves blocking histamine, a natural chemical released by the body during allergic reactions. Diphenhydramine is used to alleviate symptoms such as sneezing, runny nose, itchy eyes, and hives associated with allergies and the common cold. Beyond allergy relief, it is also used for its sedative properties to aid sleep and prevent motion sickness.
Recommended Dosage and Expected Effects
For adults, the recommended oral dosage of Benadryl is 25 to 50 milligrams (mg) every four to six hours. Most standard Benadryl tablets or capsules contain 25 mg of diphenhydramine, meaning a single dose usually involves one to two pills. Do not exceed a maximum daily intake of 300 mg. When taken as directed, expected effects include a reduction in allergy symptoms like sneezing and itching, along with noticeable drowsiness. This sedative effect is why diphenhydramine is often chosen as an ingredient in over-the-counter sleep aids.
Effects of Exceeding the Recommended Dose
Taking three standard 25 mg Benadryl pills results in a 75 mg dose of diphenhydramine, which is at the higher end of the typical single adult dose and can heighten side effects. While 75 mg might be considered within a safe single dose range for some adults, it can lead to more adverse reactions compared to the standard 25 mg or 50 mg dose, particularly for individuals who are more sensitive to the medication. Exceeding the recommended dosage can intensify common side effects such as severe drowsiness and dizziness.
Beyond these, higher doses of diphenhydramine can lead to uncomfortable and serious symptoms. Individuals may experience blurred vision, dry mouth, dry eyes, and difficulty urinating (urinary retention). An increased heart rate and heart palpitations are possible. Mental state changes can occur, including confusion, disorientation, agitation, and irritability. In severe instances, individuals might experience hallucinations.
These symptoms stem from diphenhydramine’s anticholinergic properties. Diphenhydramine works by blocking muscarinic acetylcholine receptors. Acetylcholine is a neurotransmitter involved in various bodily functions, and its inhibition leads to effects like dry mouth, blurred vision, and urinary retention. As a first-generation antihistamine, diphenhydramine readily crosses the blood-brain barrier, affecting the central nervous system. This central action contributes to its sedative effects, but in higher doses, it can paradoxically lead to central nervous system stimulation, manifesting as agitation, confusion, and hallucinations.
When to Seek Medical Attention
It is important to recognize when a reaction to Benadryl warrants immediate medical attention. If someone has taken more than the recommended dose and exhibits severe confusion, an inability to be awakened, or experiences seizures, seek professional medical help. Other serious signs requiring immediate care include an irregular heartbeat, significant difficulty breathing, or unresponsiveness. These symptoms indicate a potentially severe reaction or overdose.
In such situations, contact a poison control center immediately at 1-800-222-1222, or call your local emergency number, such as 911. Providing details about the amount of Benadryl taken, the time of ingestion, and any observed symptoms can assist medical professionals in providing guidance and care. Delaying medical attention in these circumstances can lead to more severe complications.