Benadryl

Benadryl Medication Overview

Benadryl, containing the active ingredient diphenhydramine, is an antihistamine used to relieve symptoms of allergy, hay fever, and the common cold. These symptoms may include rash, itching, watery eyes, itchy eyes/nose/throat, cough, runny nose, and sneezing. It is also used to prevent and treat nausea, vomiting and dizziness caused by motion sickness, and to induce sleep.

Dosage Forms and Strengths

Benadryl is available in various forms including oral tablets, liquid-filled capsules (liqui-gels), chewable tablets, dissolving tablets, and oral solution (liquid). The product strength varies; common oral tablet strengths are 25 mg and 50 mg.

Proper Use and Administration

To ensure the effective and safe use of Benadryl, it should be taken exactly as directed on the package or by a physician. Dosage depends on age, medical condition, and response to treatment. Capsules and tablets should be swallowed whole with water without crushing or chewing. Chewable tablets must be chewed thoroughly before swallowing.

Drug Interactions and Contraindications

Benadryl should not be used in conjunction with alcohol or other CNS depressants. It may interact with other medications that cause drowsiness such as opioid pain or cough relievers, alcohol, marijuana, drugs for sleep or anxiety, and muscle relaxants. The medication is contraindicated in individuals with hypersensitivity to diphenhydramine, narrow-angle glaucoma, bladder obstruction, peptic ulcer disease, prostate enlargement, and those taking monoamine oxidase inhibitors (MAOIs).

Special Populations Considerations

Pediatric and geriatric patients may have an increased risk of experiencing side effects from Benadryl. The elderly, in particular, may be at higher risk for dizziness, sedation, confusion, and or hypotension. Children may be more sensitive to the excitation side effect. Moreover, Benadryl is not recommended during breastfeeding due to the risk of adverse effects in the nursing infant.

Use in Pregnancy

Benadryl should only be used during pregnancy if the potential benefit justifies the potential risk to the fetus. It crosses the placenta and the outcomes of its use in pregnancy have not been established.

Allergic Reactions and Overdosage

An allergic reaction to Benadryl can include symptoms such as rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, and trouble breathing. In an overdose, symptoms may include extreme drowsiness, confusion, weakness, ringing in the ears, blurred vision, large pupils, dry mouth, flushing, fever, tremors, hallucinations, seizures, and possibly death.

Storage and Stability

Benadryl should be stored at room temperature, away from light and moisture. Do not store in the bathroom and keep all medications away from children and pets. Do not use any Benadryl product that is discolored or has any visible particles in it.

Pharmacodynamics and Mechanism of Action

Diphenhydramine operates by blocking histamine H1 receptors which prevent the effects of histamine, a substance produced by the body during an allergic reaction. It also possesses anticholinergic effects and sedative properties which contribute to its effectiveness in motion sickness and as a sleep aid.

Pharmacokinetics Detail

After oral administration, Benadryl is quickly absorbed with peak plasma concentrations reached within one to four hours. It is metabolized by the liver and excreted mainly by the kidneys. The half-life of diphenhydramine is reported to be in the range of 2.4 to 9.3 hours in healthy adults.