What is the most important information I should know about diphenhydramine?
Use caution when driving, operating machinery, or performing other hazardous
activities. Diphenhydramine may cause
dizziness or drowsiness. If you experience dizziness or
drowsiness, avoid these activities.
Use alcohol cautiously. Alcohol may increase drowsiness and dizziness while taking
diphenhydramine.
What is diphenhydramine?
Diphenhydramine is an antihistamine. Diphenhydramine blocks the effects of the naturally
occurring chemical histamine in the body.
Diphenhydramine is used to treat sneezing; runny nose; itching, watery eyes; hives; rashes;
itching; and other symptoms of allergies and the common cold.
Diphenhydramine is also used to suppress coughs, to treat motion sickness, to induce sleep,
and to treat mild forms of Parkinson's disease.
Diphenhydramine may also be used for purposes other than those listed in this medication
guide.
What should I discuss with my healthcare provider before taking diphenhydramine?
Do not take diphenhydramine if you have taken a
monoamine oxidase inhibitor (MAOI)
such as
isocarboxazid (
Marplan),
phenelzine (
Nardil), or
tranylcypromine (
Parnate) in the last 14
days. A very dangerous drug interaction could occur, leading to serious side effects.
Before taking this medication, tell your doctor if you have
You may not be able to take diphenhydramine, or you may require a
lower dose or special monitoring during treatment if you have any of the conditions listed above.
Diphenhydramine is in the FDA pregnancy category B. This means that it is not
expected to be harmful to an unborn baby. Do not take diphenhydramine without first talking to
your doctor if you are pregnant.
Infants are especially sensitive to the effects of antihistamines, and side effects could
occur in a breast-feeding baby. Do not take diphenhydramine without first talking to your doctor if
you are nursing a baby.
If you are over 60 years of age, you may be more likely to experience side effects from
diphenhydramine. You may require a lower dose of this medication.
How should I take diphenhydramine?
Take diphenhydramine exactly as directed on the package or as directed by your doctor. If
you do not understand these directions, ask your pharmacist, nurse, or doctor to explain them to you.
Take each dose with a full glass of water.
Diphenhydramine can be taken with or without food.
For motion sickness, a dose is usually taken 30 minutes before motion, then with meals and
at bedtime for the duration of exposure.
As a sleep aid, diphenhydramine should be taken approximately 30 minutes before bedtime.
To ensure that you get a correct dose, measure the liquid forms of diphenhydramine with a
special dose-measuring spoon or cup, not with a regular tablespoon. If you do not have a
dose-measuring device, ask your pharmacist where you can get one.
Never take more of this medication than is prescribed for you. The maximum amount of
diphenhydramine that you should take in any 24-hour period is 300 mg.
Store diphenhydramine at room temperature away from moisture and heat.
What happens if I miss a dose?
Take the missed dose as soon as you remember. However, if it is almost time for the next
dose, skip the missed dose and take only the next regularly scheduled dose. Do not
take a double dose of this medication unless otherwise directed by your doctor.
What happens if I overdose?
Seek emergency medical attention if an overdose is suspected.
Symptoms of a diphenhydramine overdose include extreme sleepiness, confusion, weakness,
ringing in the ears, blurred vision, large pupils, dry mouth, flushing, fever, shaking, insomnia,
hallucinations, and possibly seizures.
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