About diphenhydramine hydrochloride
First-generation antihistamine
Used for
- Relief of allergy symptoms, such as sneezing, itching, and runny nose
- Short-term treatment of occasional sleeplessness
- Relief of motion sickness symptoms
Usual adult dose
Allergies: 25–50 mg every 4–6 hours; maximum 300 mg daily. Sleep: 50 mg at bedtime.
Usual dose in children
Allergies: ages 6–11, 12.5–25 mg every 4–6 hours; maximum 150 mg daily. Not for children under 6 without medical direction.
Common side effects
- Drowsiness and dizziness
- Dry mouth, blurred vision, or constipation
- Difficulty urinating
- Confusion, especially in older adults
Important warnings
- Can impair alertness; avoid driving if drowsy.
- Avoid alcohol and other medicines that cause drowsiness.
- Older adults may have increased confusion, falls, and urinary problems.
- Overdose can be dangerous; keep away from children.
Pregnancy
Use only when needed after discussion with a healthcare professional; pregnancy safety information is limited.
Breastfeeding
May cause infant drowsiness or irritability and may reduce milk supply, especially with repeated use.
Interactions
- Alcohol, opioids, sedatives, and sleep medicines increase drowsiness.
- Monoamine oxidase inhibitors can intensify side effects.
- Other medicines with anticholinergic effects increase dry mouth, constipation, and urinary problems.
AI-generated from general medical knowledge, not from this product's official leaflet. It may be incomplete or out of date. Not medical advice — ask a pharmacist or doctor before making any decision.