Benadryl, known generically as diphenhydramine, is a common over-the-counter antihistamine. It is widely used to alleviate symptoms associated with allergies, such as sneezing, runny nose, and itchy eyes, and can also help with cold symptoms. A common side effect is drowsiness. For safety and effectiveness, adhere to recommended dosages.
Benadryl’s Purpose and Standard Dosage
Benadryl is classified as a first-generation antihistamine. It blocks histamine H1 receptors, preventing allergic responses like itching and sneezing. Because it can readily cross the blood-brain barrier, Benadryl also affects H1 receptors in the central nervous system, leading to its sedative effects. This interaction with receptors also contributes to other anticholinergic side effects like dry mouth.
The standard adult single dose for Benadryl is 25 milligrams (mg), though some indications allow up to 50 mg. This dose is taken every four to six hours as needed, with a maximum daily intake of 300 mg. At this recommended dosage, common effects include drowsiness, mild dry mouth, and relief from allergy symptoms. It starts working within 15 to 60 minutes and its effects last for about four to six hours.
Consequences of a Double Dose
Taking two Benadryl tablets at once significantly amplifies the drug’s effects. This double dose can lead to more pronounced drowsiness and dizziness, which can impair coordination and increase the risk of falls or accidents, such as impaired driving. Other common side effects like dry mouth can become more intense, and individuals may experience blurred vision. Less common but possible side effects include difficulty urinating or constipation.
While a single double dose of Benadryl may not be life-threatening for most healthy adults, it increases discomfort and can lead to disorientation or confusion. Some individuals, particularly children, can experience a paradoxical effect where they become hyperactive or agitated instead of drowsy. The body’s response to diphenhydramine can vary based on individual factors like age, other medical conditions, and concurrent medications. For example, older adults are more sensitive to side effects such as sedation, dizziness, and low blood pressure, which further increases their risk of falls.
Recognizing Serious Reactions and Overdose
Recognizing a serious reaction or overdose to Benadryl requires immediate medical attention. Warning signs include severe confusion, agitation, or delirium, along with hallucinations. Other concerning symptoms are seizures, a rapid or irregular heartbeat (tachycardia), and extreme drowsiness where the person is difficult to rouse. Difficulty breathing is also a serious sign requiring immediate concern.
If any of these serious symptoms occur, seek immediate medical help. Individuals should immediately call poison control at 1-800-222-1222 or contact emergency services, such as 911. If the person has collapsed, is having seizures, has trouble breathing, or cannot be awakened, calling 911 is the immediate action. Even if symptoms are not immediately life-threatening, contacting a healthcare provider for advice is advisable when concerns about dosage or unusual reactions arise.