What Factors Affect Benedryl® Dosage?

One of the first antihistamine medications ever developed, Benedryl® is still used as an over-the-counter treatment for allergies. Benedryl®'s powerful sleep-inducing side effects have led to its use as a short-term treatment for acute insomnia as well as its inclusion in medications like TylenolPM®, Nytol®, and Unisom® for the discomfort of common colds. The drug is also used for its anti-vomiting properties in the treatment of motion sickness and as a treatment for anaphylactic reactions when the use of epinephrine is contraindicated. The appropriate Benedryl® dosage level may vary from patient to patient according to factors, such as his or her age, the condition to be treated, and the condition's severity.

When treating the symptoms of seasonal or chronic allergies in adults, the recommended initial Benedryl® dosage is 25 to 50 mg taken three to four times daily. Due to its sedative effects, Benedryl® should not be used if piloting a motor vehicle or if taking alcohol or other central nervous system depressants. In children over 12 years old, a Benedryl® dosage of 25 to 50 mg should be administered every four to six hours, with the total daily dose not in excess of 150 mg. Patients between the ages of two and six years old should be given 6.25 mg every period of four to six hours and no more than 37.5 mg per day, while those between six and 12 years old should receive between 12.5 and 25 mg in the same time period up to 150 mg daily.

Adults being treated for insomnia should receive a Benedryl® dosage of 25 to 50 mg immediately before retiring to bed. Children over the age of 12 may take the same dose given to adults. As of 2011 there is no recommended Benedryl® dosage for children under 12, as the drug has not been conclusively researched for insomnia in this population.

While Benedryl® has not been found to be effective in the treatment of motion sickness after onset, it may be effective in preventing vomiting if administered 30 minutes beforehand. Adults should be given a dose of 25 to 50 mg every six to eight hours, redosing before meals and bedtime. The same Benedryl® dosage recommendations apply to children over 12 up to a maximum daily dose of 150 mg. Children between the ages of two and six should receive no more than 37.5 mg daily in 6.25 mg doses given every four to six hours, while those between six and 12 should receive no more than 150 mg daily in doses of between 12.5 and 25 mg with the same frequency.