Since it does not require a prescription, many people who have acute insomnia use it to help initiate and maintain sleep. Due to the potential for side effects, especially among older people, other initial approaches for managing insomnia are often recommended.
Uses
Diphenhydramine has many potential uses. It causes sleepiness, and it is sometimes recommended for short-term treatment of insomnia or acute insomnia. By definition, this is insomnia that occurs for less than three months.
It is one of the ingredients found in multiple sleep aids:
Tylenol PM Advil PM Aleve PM ZzzQuil Benadryl
It may help you get to sleep or stay asleep. However, it may cause sleepiness the day after taking it.
In addition to its use as a sleep aid, diphenhydramine is often used to relieve allergies or treat allergic reactions, and it can be helpful in preventing motion sickness. It is also used to alleviate extrapyramidal symptoms, which may occur as a side effect of some medications.
How It Works
Diphenhydramine is part of a class of medications called antihistamines. It works at the level of neurotransmitters, which are the chemical messengers within the brain.
It causes its sedative effects by allowing histamine, a neurotransmitter, to build up in the synapses, which are the spaces between nerve cells. Diphenhydramine specifically blocks the uptake of histamine into nearby cells.
Diphenhydramine works both centrally within the brain as well as in peripheral nerve cells in other parts of the body. It also can suppress a cough, nausea, and uncontrolled movements called dyskinesis.
Precautions and Contraindications
Children younger than 2 years old should not use diphenhydramine. Additionally, caution should be used when this medication is used by children younger than 6 years old and by the elderly.
If you have increased intraocular pressure, such as in glaucoma, you should use caution with diphenhydramine.
Other conditions may also require caution, including:
AsthmaBowel or bladder obstructionChronic obstructive pulmonary diseaseHeart diseaseHigh blood pressureHyperthyroidismPeptic ulcer diseasePneumoniaProstate enlargement
If you have these conditions, it’s important to discuss your risk with your healthcare provider before starting to use the medication.
Side Effects
Some side effects that may commonly occur with diphenhydramine include:
Delirium (confusion)Diminished coordination or cognitive functionDrowsinessDizzinessIncreased intraocular pressure (similar to glaucoma)HeadacheStomach discomfortThick lung secretionsDry mouth or noseHyperactivityConstipationDifficulty urinatingLow blood pressureBlurry or double visionRapid or irregular heart rateSensitivity to lightSweatingErectile dysfunction (impotence)
Severe
There are also risks of serious side effects. These occur more rarely.
When using diphenhydramine, serious side effects may include:
Anaphylaxis (severe allergic reaction including difficulty breathing)Low blood cell counts (agranulocytosis, anemia, thrombocytopenia, and leukopenia)Abnormal heart rhythmsSeizuresToxic psychosisAcute labyrinthitis (inner ear problems)
Warnings and Interactions
People who have certain conditions should use diphenhydramine with caution, or not at all. It is an over-the-counter medication, so the risks are thought to be slightly lower compared to prescription medications.
Diphenhydramine has the potential to interact with some other drugs, especially those that affect the brain, so you may wish to review your medications with your healthcare provider or pharmacist before use.
A Word From Verywell
If you’ve been experiencing chronic insomnia that occurs at least three nights per week and lasts at least two weeks, talk to your healthcare provider. You might also consider the use of cognitive behavioral therapy for insomnia (CBTI) to resolve the condition instead of medication.
You can use our Doctor Discussion Guide below to start a conversation with your healthcare provider about the most appropriate treatment approach.
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