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July 12, 2019

Diphenhydramine is an antihistamine used to relieve irritated, red, itchy, watery eyes; sneezing; runny nose due to:

It is also used to treat and prevent vomiting, nausea and dizziness due to motion sickness. It is often prescribed by doctors to help you relax and fall asleep. The over-the-counter medication is a good initial option for the short- term treatment of acute insomnia. It is also used to control abnormal movement in people who have early stage parkinsonian syndrome. However, this medication will only help relieve the symptoms of these conditions. It will not treat the cause of the symptoms or speed up the recovery.

This medication works by blocking the natural substance called histamine that the body makes when it reacts to allergens. The drying effect such as runny nose and watery eyes are caused by blocking the acetylcholine in the body. 

When and How to Use Diphenhydramine

Diphenhydramine comes as a capsule, tablet and liquid form to take by mouth.

  • The typical dose for the treatment of allergic reaction in an adult is 25mg to 50mg every 4 to 6 hours. The maximum recommended dose is 300 mg a day.
  • For children 6 to 11 years of age, the dose is 1 tablet every 4 to 6 hours or 5ml to 10 ml every 4 to 6 hours. Use the measuring cup or spoon and not the household spoon.
  • For the treatment of insomnia, the dose is 50 mg. Take it 30 minutes before bedtime.
  • To prevent motion sickness, take your dose 30 minutes before travel.

Read the dosing instruction found on the product label. Do not change your dose or take this medication more often than directed.

Possible Side Effects of Diphenhydramine

Common side effects of this medication are:

  • Headache
  • Nausea and vomiting
  • Drowsiness
  • An increased chest congestion
  • Muscle weakness
  • Constipation

Serious side effects are:

  • Blurred vision
  • Difficulty urinating

Getting the Best Result from Diphenhydramine

  • This drug can make you drowsy and may blur your vision. Use it with care.
  • If you continue to have difficulty sleeping for longer than 2 weeks, consult your doctor right away.
  • Do not use this medication with other antihistamines.
  • Avoid drinking alcoholic beverages when taking this medication. Alcohol can increase drowsiness. Avoid using this medication if you are breastfeeding.
  • This medication may cause a decrease in mental alertness. Use this with caution especially if you are driving.
  • This product is not suitable for children under 6 years of age.
  • Children who use this medication may be more sensitive to the side effects. The drug can cause excitement instead of drowsiness in young children.

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