Diphenhydramine

Overview

Its medication class is First-generation antihistamine. Common uses include Allergy symptoms and OTC sleep-use in some settings. Product forms and labels can differ, so follow the specific package instructions and ask a pharmacist or qualified healthcare professional about individual questions.

How to Take it

Route

Oral tablet/liquid.

Time of day

Best taken in the evening/bedtime; avoid driving after dosing.

With food/water

Water with or without light food, esp. if stomach upset.

Preparation

Take only one labeled product at a time.

Safe dose

Use the lowest dose for age and indication.

Max dose

Do not exceed label daily cap.

Frequency

Every 4–8 hours when needed unless adverse drowsiness occurs.

Other recommendations

Avoid alcohol and other sedatives; do not combine with sleep aids without guidance.

Common uses

• Allergy symptoms and OTC sleep-use in some settings

Common side effects

• Sedation
• dizziness
• dry mouth
• blurred vision
• constipation
• urinary retention
• nausea
• rash
• and confusion

Important warnings

• Strong sedative and anticholinergic effects—avoid driving, alcohol, opioids, tranquilizers, or other sleep medicines. Avoid in glaucoma, prostatic hypertrophy/urinary retention, severe asthma, GI obstruction, or seizure disorders. Not for routine pediatric use; overdose can cause agitation, delirium, seizures, and respiratory depression. Do not combine with other diphenhydramine-containing products.

General interactions information

Additive CNS depression with alcohol, opioids, sleep medicines, anticholinergics.